Acqua of the Back

Acqua of the Back (後方のアックア), real name William Orwell (ウィリアム＝オルウェル), is a character introduced in Toaru Majutsu no Index. A strong and willful man, he is a mercenary of renown in England, and originally a Saint of terrific power. He was a member of God's Right Seat, and is one of the few characters who easily defeated Kamijou Touma in combat.

After the events of World War III and the dissolution of God's Right Seat, he is once again referred to using his real name.

Etymology
Acqua's assumed name is the Italian word for "water".

Appearance
Acqua of the back is a man with tea-colored hair, and is described as having a straight-lined face that looked like chiseled from stone. His muscular look is a mark of him going through many bloody and gory battles, and not the ones that a body builder has. This is unique from the other God's Right Seat since the others are rather thin due to their fighting style.

He wears a shirt that looked similar to a polo shirt with blue as the base, as well as blue pants. This is likely part of his magic as he is aligned to Archangel Gabriel, which rules over the color blue.

Personality
Despite calling himself as neither a good man or a philantrophist, Acqua of the Back has a unique code of ethics that he follows steadfastly. He is confident in the rightness of his actions and will not find excuses for it what he does.

When it comes to combat, he will allow his enemies to follow his conditions of surrender and let them live, as he did with allowing Touma to live if he gave his right hand to him. He doesn't like cheap tricks and would rather face his enemies head on. In fact, he loathes those who kill civilians, as Terra of the Left can attest. Moreover, he dislikes looting on the battlefield. Although he loves a good battle from worthy opponents like the Amakusa Christians and Kanzaki Kaori, he is willing to forgo battle, and by proxy killing his enemies, if there is a possibility not killing at all. It is not like he doesn't want to kill his enemies, it is just that if there is not a need to then he won't kill. Indeed, he didn't kill the Amakusa Christians at first because they weren't the ones he needed to take down. When in combat, he recognizes that there are only allies and enemies on the battlefield, and will do his uttermost to defeat his enemies in battle. In spite of this, he still loathes or at least pities those who are incapable of fighting an equal level to him. He is also gracious in defeat, willing to accept it as well as face it head on.

He shows respect for courage, resolve, and the will to protect others, aspects that he found in Touma, among others. In his own way, he also values friendship, as he had with Knight Leader, though that wouldn't be enough to stop him from doing his mission.

Overall, the man follows his own code of honor. He is quite aware that civilian sacrifices might be needed in the battle, but goes out of his way to lessen them. Prior to joining God's Right Seat when he was still a mercenary, he taught people who have been caught in battle zones knowledge of herbs to lower mortality rate and taught villagers how to cook meals. He is also very active outside the battlefield, and in some places people call him a Sage. He is willing to pay for his own crimes, as what had happened when he willingly went to the Tower of London after the War. He doesn't seem to hold grudges towards the people he's fought against and is willing to work with them. Finally, of all the God's Right Seat, he is the only one who shows respect to authority, which in this case was the Pope.

Acqua of the Back also cares for his homeland, Great Britain, as is the reason why he chose not to become a member of the Knights of England as he believes that he can watch it over from the outside, without the chains of institution, while his friend the Knight Leader can protect it from the inside.

Acqua of the Back enjoys drinking, along with the Knight Leader.

Background
William Orwell was born in England, and was baptized in an Anglican church. He was a Saint and had the inherent potential of what would later be known as Divine Mother's Mercy, which would later blossom after becoming a member of God's Right Seat. He is a magician and a mercenary. As a mercenary, he was a lone wolf, specializing in taking down enemy strongholds, and he working primarily in England, though could be hired and find work any part of the world. His work took him from France, where he destroyed the Knights of Orleans, to the snowy lands of Russia, where he aided the Divination Operation Brigade. Even then, all his mercenary work benefitted Great Britain. He had some connections from the British Royal Family, and as such, when he was requested to do something, he couldn't refuse it completely.

Having a friendship with the Knight Leader, and likely due to his work as a mercenary and ability as a magician, asked him many times to join the Knights of England. He finally yielded when he was warmly invited by the British Royal Family, albeit begrudginly, and had his arms designed to symbolize his feelings of being chosen as a knight. Moreover, even Buckingham Palace was making space for William's knighthood, giving him a spot in a hall for his arms to bore alongside other knights.

However, he was still wary of being chosen. Moreover, he saw that becoming a knight would confine him to the tethers of the institution as the internal politics and etiquettes of the organization prevent him from doing what he wants and needs. He became aware that the British Royal Family are slowly being corrupted, and is also wary of the Anglican Church's influence on them as it was being controlled by Laura Stuart. Ten years prior to the start of the story timeline, William singlehandedly ended the Princess Villian hostage crisis, as the political intrigue that the British Royal Family played prevented the Knights of England from rescuing Princess Viliian themselves from the Spanish Astrological Sect. William reveals his intentions of leaving England to protect it from the outside while the Knight Leader protects it from the inside. In spite of this, a space still remained for William in Buckingham Palace, and his escutcheon, though stopped in its production, was kept in well condition by the manufacturer due to his respect for William's work in England.

Three years prior to the start of the story timeline, William fought another Saint. It is unknown what the outcome of the battle was or if the other Saint is still alive. William joined God's Right some time prior to the start of the story timeline, and was then known as Acqua of the Back. There his inherent potential of having Divine Mother's Mercy finally blossomed, as well as becoming aligned to Archangel Gabriel, making him an even more powerful magician.

Arms
As a prospective member of the Knights of England, William Orwell was allowed to specify the design of his escutcheon (盾の紋章 (エスカッシャン)), that should symbolize the bearer's family background, family history, and identity. The design of his escutcheon is unusual and mirrors his feelings after being chosen as a knight. There are two main colors, blue as base and green as decoration, though this is unusual as green is normally used as a base color as well and not as decoration. The escutcheon is divided into 4 parts, and there are three charges, all mythical creatures, as in "they don't exist in real life": the dragon, unicorn, and selkie. These charges represent not only England but all of the Great Britain, England, Scotland, Wales, and Ireland. According to Sherry Cromwell's analysis, William was unhappy about being chosen as a knight and reflected his feelings through his escutcheon, making fun of others through it and explicitly wanting people to have no choice but to laugh at his coat of arms. Acqua of the Back would later have this escutcheon emblazoned on Ascalon. The Knight Leader would later interpret the escutcheon differently, with the blue foundation representing the nations of the United Kingdom, and the charges as the Royal Family, the Knights of England, and the Anglican Church, the entirety of it representing the complete harmony of the organization known as the United Kingdom.

Below is the approximate description of William's escutcheon in real world blazon:

"Per saltire, azure and ciel dancetty, azure and ciel lozengy, ciel and azure paly, ciel and azure chequy, a saltire gules within a bordure gules, dexter chief wyvern statant seen from above, sinister to dexter selkie rampant, and dexter base unicorn statant seen from above facing each other, all vert."

Academy City Invasion Arc
His first appearance is at the end of this arc, when he picks up Vento after she is defeated by Touma. He tells Touma that the Invasion is over and the people affected by Vento's divine punishment would recover soon. However, when Touma presses the issue further, he tells Touma that he is a saint and that Touma should not even try to fight him, and he leaves. While leaving Academy City, he also receives a call from Terra regarding his next course of action.

Document of Constantine Arc
Sometime before the beginning of the October riots, Acqua of the Back, along with the Pope, comes upon Terra of the Left drinking cheap wine, trying to replenish his strength. Acqua of the Back comments on Terra's taste on using cheap wine and is later scolded by the Pope for smirking at Terra's joke regarding his knowledge of wines despite being a mercenary. Terra of the Left prepares to leave, intending to use the Document of Constantine to cause mayhem among the constituents of the Church against Academy City in order to draw the Russian Orthodox Church to their side. Acqua of the Back objects to the use of civilians, but Terra of the Left states that it would be unnatural not to use the Church's vast human resources, much to Acqua of the Back's chagrin. Terra of the Left later leaves, and the Anti-Academy City October riots begin.

Acqua of the Back later receives disturbing reports of children and sight-seers being used by Terra of the Left in order to make alignment adjustments to his Execution of Light spell. Later, Terra of the Left returns to the Vatican and meets up with Acqua of the Back in St. Peter's Basilica. Even though the Document of Constantine was destroyed, Terra is satisfied with the results at the Russian Orthodox have been forced by the recent events that have transpired to ally themselves with the Roman Catholic Church. With the sides finally drawn for the War, Terra says that they should discuss how to move their troops from here on with Fiamma of the Right, and states that he wants to observe Academy City's repsonse as well as the Imagine Breaker. Before he leaves, Acqua of the Back asks him if the information he has received that he used children and tourists on the outskirts of Rome to make some alignment adjustments for his Execution of Light spell. Terra of the Left responds callously and bluntly, and says that he did. He asks Acqua if such a thing is worth bringing up, to which he responds if Terra wasn't supposed to act in order to save of humanity without discrimination. Terra says that he is doing so, but states that pagans are not even human, and states that he made sure that the targets for his alignment adjustments were not believers in the Roman Catholic Church. Terra is annoyed about the subject Acqua is bringing up as he is too busy with trying to improve his spell.

Suddenly, Acqua of the Back takes a pillar from the basilica and smashes Terra of the Left in half. Terra is still alive and tried to use his spell to close his wounds but is unable to. Despite slowly dying, Terra's expression remained calm, believing that even if he died, in the end he would be chosen by God in the Final Judgment and led to the Holy Kingdom. Seeing Terra's expression, Acqua tells Terra that there is no way he would be chosen by God, and mocks him for still being deluded, stating that the only place he'll be going to will be Hell. Terra is able to comprehend Acqua's words, turning his once calm expression to that of scorn. There, Terra of the Left dies.

The Pope then arrives and tells Acqua of the Back to be careful on not destroying the St. Peter's Basilica, not just because of aesthetic and historical reasons, but also because of its importance in defensive functions. Acqua then states that the problem in organizations, that there is always someone out of control in it, and cites God's Right Seat and Terra of the Left as an example. He tells the Pope that it is not enough for God's Right Seat to achieve its goal and become La Persona Superiore a Dio for his desire to save more believers, and states that in order for God’s Right Seat to continue functioning as it should, it needs someone outside of it to watch over it and to guide it. Acqua of the Back tells the Pope that he is the one most suited for that position. The Pope smiles and says that when he first heard about God's Right Seat, he was overjoyed that there was such a quick way of guiding believers. However, he then states that he realized that God does not wish for an easy path to salvation, and comments on how the Father watching over him truly likes trials and tribulations. The Pope then asks what his next move will be, to which Acqua of the Back comments that there is only one option after Terra was purged and Vento still recuperating. The Pope asks if he is going to attack Japan via Russia as Terra suggested. Acqua of the Back states that civilians should not stand on the battlefield, and that only soldiers need to cross swords, implying to the Pope he will act himself.

Acqua of the Back Arc
Acqua of the Back is the primary antagonist of this arc. After killing Terra of the Left, Acqua of the Back wraps his corpse in a luxurious box. Acqua the sends letters of challenge to both Academy City and the Anglican Church, telling them that he will crush Touma himself and dares them to use all of their power if they intend to stop him. The recipients receive two days prior to the start of the arc. The box is sent along with the letter to the Anglican Church to convince them that the letters are legitimate, and Itsuwa is then called to confirm Terra of the Left's identity, having fought him in Avignon.

For the earliest parts of the arc, Acqua of the Back is a seemingly distant but palpable threat to Touma and the Amakusa Christians, as the former triest to go on with his everyday life. Acqua of the Back's presence is first alluded to when the Amakusa Christians guarding Touma from afar feel constricted, and discover that the Amakusa Christians are the only ones who are walking in the street. Tatemiya Saiji then orders prepares his comrades for battle but they are too late, Acqua of the Back utterly defeats them, though doesn't kill them as they're not the ones he intends to kill.

Back with Itsuwa and Touma, the both of them are unaware that Acqua of the Back has appeared before the Amakusa Christians and utterly defeated them. They later move to a bridge, and after Itsuwa blushes at the thought of them being alone together, they note their queer situation. There is literally nobody other than the two of them. And there came steps from the darkness and it showed Acqua of the Back. He reminds them of his warning, but since they've chosen this path he tells them that he will use all of his strength to crush them. Acqua of the Back says to him that he has come to crush him, the reason for all the unrest in the world. Touma calls him out on this, and references what they did to Avignon. But Acqua would not yield, and points that what happened there only happened because of Touma and his Imagine Breaker. He then tells Touma to hand over his right hand if he wants him to spare his life. Itsuwa asks about the Amakusa Christian, to which Acqua says that he did not kill them for what he wants is not them. Despite Touma and Itsuwa's concentration, they are caught unawares. Acqua sends Itsuwa flying with a single hit, allowing him to attack Touma with his giant mace that he summoned. Fortunately, Itsuwa somehow flings her bag between them, sparing Touma for the moment from the large mace despite the debris hitting him. But the sheer power of the blow flings Touma high up and then hitting the metal frame of the bridge, making him fall. Itsuwa hastily assembles her Friulian Spear, and she prepares to fight despite being damaged from the previous attack. Acqua of the Back points out the folly of challenging the man whom her entire group couldn't beat, but Itsuwa would not yield. Seeing this, Touma tries to stand but is unable to as Itsuwa and Acqua fight in high speed. But it is quickly over as it had begun, and Itsuwa is hit with the mace and then tossed towards Touma, hitting him. Touma understands the situation, which he could not hope to match against Acqua even after he fought Vento of the Front and Terra of the Left. Acqua of the Back once again asks for his right hand, but Touma doesn't cooperate, prompting Acqua to attack him again.

Itsuwa regains consciousness after Acqua of the Back pummels Touma to the point of drawing blood. Touma appears before a bloody mess. She is horrified by this, at which point Acqua notices her, telling her to move or she'll be caught by the tremendous power of his attack on Touma. Itsuwa breaks down and desperately tries to heal Touma in spite of his right hand. But it is vain due to the Imagine Breaker, and Itsuwa can only cry. Acqua of the Back tells her that it is enough, and steps on her back, silencing her cries and moans. As Acqua tries to come towards Touma, a screaming Itsuwa raises up her arms against Acqua again, trying to protect Touma. Acqua sighs as he and Itsuwa prepare for the inevitable conclusion of their clash. However, before Acqua can strike him down, Touma once again stands by her side. He thanks Itsuwa for the healing magic despite her knowing it did not work, and in her shock, cannot stop him from going towards Acqua of the Back, to protect her. To save Itsuwa, Touma alone stand against Acqua, impressing him. Acqua of the Back deals a horrendous blow upon Kamijou Touma, but does not kill. Touma is hung upon the mace. Acqua of the Back smiles at Touma's courage, and tells Itsuwa that he is giving them one day more. He tells her that he will give them one more day to choose whether or not to give Touma's right hand, and if they did, he will spare their life. Afterwards, Acqua swings his mace that had Touma on it, flinging from the bridge and into the cold water at high speed, and finally sinking after bouncing from it several times. Without confirming whether his target is dead, Acqua turns his back on Itsuwa for one day more.

While waiting for the appointed and the Amakusa Christians, Acqua of the Back is in a nature park on the third level of School District 22, speaking to the Pope using magic through a phone, likely to disguise it. He warns the Pope that despite being in the park away from all the technology, there is still a chance that they're being spied on like the Amakusa Christians. The Pope asks about Acqua of the Back not killing Touma but just taking his right hand, saying that he recalls Vento of the Front telling him that God's Right Seat won't change their goals. Acqua of the Back however tells him that is a problem in Vento of the Front's character as God's Right Seat change according to how the situations plan out, and Terra of the Left himself went overboard. Pope tells Acqua of the Back that what he is doing now is the better method. However, he says to him that if Touma really intends on defying God, they need to kill him, though says that since Touma isn't all familiar with God he is against killing it because of this reason, which Vento of the Front. Acqua of the Back tells the Pope that he is neither a good man nor a philanthropist, saying that if it comes to the point where he needs to kill Touma he will still do it, though there is still a possibility that he doesn't need to kill at all. The Pope then relates on how though God's Right Seat was set-up as a negotiating tool to enter the enemy's stronghold, he can only watch from the Vatican. After pondering the purpose of God's Right Seat in the Roman Catholic Church, Acqua of the Back tells the Pope that the next time he contacts him it will all be over, and that whether the target will still be alive after that then he'll tell him later.

His endeavors have allowed him to move to quite a bit of distance from the park where the Mimosa first attacked him. Just before the Amakusa confront him, Acqua of the Back has taken down a total of 8 self-propelled Mimosas, 17 armored vehicles, 38 androids, all unmanned. His battle is also noticed by the Amakusa Christians as they regroup.

By 3 AM in the morning, Acqua of the Back's little excursion has led him to a metal bridge in School District 22, a deliberate choice of his as he attempts to find a human controller to no avail. Academy City forces later retreat after an hour of fighting. Seeing this, Acqua of the Back admits that his enemies are not as tactless and dumb as he expected. Acaqua of the Back tells himself that it would have been easy if he had Vento of the Front's Divine Punishment. Acqua of the Back then checks on the time and sees that there is still 19 hours left before the Imagine Breaker deal, but there was not time to wait as he sees that the Amakusa Christians have already made their decision as they approach him.

He asks them if they are prepared for it, to which Saiji says that it is because he gave them a tough question they couldn't decide on and as such quickly settled it. Hearing this, Acqua of the Back then summons his large mace before them. He warns them that they are against the 2 billion followers of the Roman Catholic Church, and losing a single arm just so they can escape should be a bargain. Saiji says that the Church isn't the enemy but people like him who treat ordinary people as bait and manipulate them when they continue to believe in God, though Acqua of the Back just scoffs at this reply. He says to them that he isn't bothered by their decision and on the contrary, it is them that should be worrying as they gave up on their only chance at surviving. He reiterates by pointing out that he is one of the Saints and is a member of God's RIght Seat, though he says he is willing to face all of them and look forward to it if they continue to defy him and protect Touma even after hearing all of those. He then says that at the end that he will win. As he prepares to attack them, he says that is hoping that they would at least force him to use his trump card, but before he could finish he is attacked by Itsuwa with magic, creating a powerful explosion. This surprises Saiji, though Itsuwa does not respond to him as she faces an unhurt Acqua of the Back telling her that she should have listen to people's words until the end. However, Itsuwa is having none of it, and says that if he has something to say then he should say it later after he beat him to a pulp and if his jaw isn't broken. The males are in awe and shock at her action while the females are silent, intrigued by her actions.

Itsuwa ignores the commotion, continuing instead to glare at Acqua of the Back. He is impressed by her bravery but asks her if she can back her words with action. Itsuwa says that even if they are reduced to "slice of meat" they'll let him regret it all he did after beating to a meat pulp. And with the cries of her comrades regarding her outrageous claims, Itsuwa and Acqua of the Back clash in battle. Itsuwa was the one who contended against Acqua of the Back directly, while the rest of the Amakusa Christians support her by continuously changing the focal point, it was a spell that increases visual activity and mobility, allowing for Itsuwa to match up to Acqua of the Back's speed. After he begins catching up to Itsuwa, the Amakusa Christians the planted wires around him, though his strength allowed him to resist a little, they eventually activated the spell, and Acqua of the Back's body is engulfed in a red mist prison that explodes from within. And yet Acqua of the Back continues persisting, referring to his Divine Mother's Worship which allows punishment upon him to be weakened, basically making their attacks meaningless. Acqua of the Back then tries to attack, forcing the Amakusa Christians to retreat.

They later regroup 300 meters away from the metal bridge where they fought Acqua of the Back. With Acqua of the Back always breaking their formation, Saiji concludes that they should better use the weakness of the Saints, since they have properties similar to the Son of God, then they will be weak to things that have similar properties to those that have executed him. Feeling Acqua of the Back coming, Saiji tells his comrades to get into position, they create an entrance to the space between the third and fourth level, a hydroelectric turbine power plant. Saiji and the others set-up wires and trap spells down below in order to delay him long enough for them to set-up their counter against him. With Acqua of the Back's arrival, Itsuwa becomes the focal point of their formation once again. Here, Itsuwa discovers that despite being a member of God's Right Seat, he is still able to use normal spells due to his Divine Mother's Worship. Thus, being aligned to water, Itsuwa runs for her life as everything around her is a weapon for Acqua of the Back. Itsuwa is later blown down the screen that acts as the 4th level's sky. Both draw their weapons, and Acqua of the Back prepares to end the battle, however, the other Amakusa Christians finally arrive through the entrances. Battered and injured, the Amakusa Christians face down Acqua of the Back. While Itsuwa fights Acqua of the Back directly, other members attack him in every direction, however, they are still no match for his impeccable power, blowing them away. Acqua continues his attack and swings down upon Itsuwa, who barely escapes by using her sweater as a scapegoat. Itsuwa trades blows with Acqua of the Back, but the both of them know that she is getting slower. The other members support her by attacking once again in all angles, but they are once again blown away. While Acqua of the Back is busy, Saiji calls out to Itsuwa if the spell is ready yet, but their conversation is quickly interrupted after as Acqua of the Back attacks him. Saiji manages to block the strike but is still blown away by him. Acqua of the Back presses on with the offensive, slowly sapping Itsuwa's strength and endurance blow by blow they trade. However, as he moves, he soon discovers that the spell that allows him to glide and move in extreme speeds have been mixed in with some substance by the Amakusa Christians, moreover, the shockwaves brought about by this disruption rips apart the screen that he is standing on. With this gap, Itsuwa smiles and charges forward with her spear, seeing this, Acqua of the Back dodges for the first time in their battle. He jumps up, but that is enough for Itsuwa, who calls out to her Saiji and the rest of their comrades. They respond and redo their formation again with Itsuwa being the focal point. With the tube spear to reduce the friction between the spear and palm, Itsuwa strikes Acqua of the Back with her spear. It turns into lightning in the shape of a cross, the execution method that was used on Son of God, therefore the weakness of the Saints that has their bodies having the same properties as that of the Son of God, strikes down on Acqua of the Back. It was the Saint Destroyer, the culmination of the Amakusa Christians efforts to truly know their Priestess, Kanzaki Kaori, a Saint herself, in order for them truly be by their side.

But not a scratch came upon Acqua of the Back, for he had grabbed Itsuwa's spear before it hit and modified and weakening it. Slightly impressed, Acqua of the Back tells them that if he was a mere Saint then it would most likely finish him off, if not for the fact that he is also a member of God's Right Seat. He then blows her down to the 4th level, ripping the screen up. As she falls, Itsuwa and the others use barrier spells for her descent, but this was not enough, and Itsuwa falls to the floor below. Bored of the battle, Acqua descends down to her and asks Itsuwa if she is willing to hand Touma's right hand over to him or choose being killed. But Itsuwa answers with her actions, standing up once again to challenge him. Seeing this, Acqua of the Back summons the water from the 4th level and forms it into a hammer. He tries to strike it down upon Itsuwa, but ceases before doing so. Acqua of the Back notices something and disperses the spell. He tells her that she should thank her master and leaves, for Kanzaki Kaori has arrived to challenge him. About 200 meters away from where Itsuwa landed, Kaori faces Acqua of the Back. He notes that he has heard that she hates fighting, and asks her if she has any intentions of fighting against him, to which Kaori says that she will. Kaori explains that it is her personality and it is borne by her magic name, and seeing her comrades being beaten one by one, she cannot allow it carry on. She then says that she will not allow their efforts, Touma and the Amakusa Christians, to go to waste. Thus begins the battle against Saint and Saint.

And so the two Saints clashed and their weapons met in flashes and explosions and in great speeds, displaying their awesome power, and the ground shook as they stood. And they exchanged magic magic and the other countered them with their own as if the both of them knew just as much as the other. And for Kaori who has knowledge of spells from different religions, made great use of it against Acqua of the Back. Acqua of the Back note on how much she and the Amakusa will go through for the sake of Touma, impressing him. However, he warns that since she has become his enemy it has been already determined that she will be defeated by his hand. Then Acqua of the Back sends out a large pillar of water from the nearby stream and smashes it down upon Kaori, whom easily cuts it down with the power of Nanasen, nothing that she will be insulted if he thinks that is all her full power. With that she uses Nanasen to assault him in all angles, and though he can easily respond to them, Kaori made it so that the wires formed a magic circle, activating a magic spell and engulfed his entire body with flames. After three explosions, Kaori assaulted him with a slash of her blade. But he escaped though not wholly for there was a cut on his face, the first time since the battles in School District 22 against him began.

Unperturbed by this, he notes on how she and the Amakusa Christians are similar, though the difference between them is because she had talent. Using the blood from his wound he wrote down something on his mace. Although stunned because of his words for a moment, Kaori then tells him that she hopes that she can correct his words, and sheathed back her sword into its scabbard, in preparation of drawing it back again. She tells them that though they can't do things like the Yuisen, they know a few other things as well that have been passed down the ancestors of the Amakusa, concluding that these weren't made by talent but by the result of history. She tells Acqua of the Back that Amakusa is her school, her teacher, and comrades, and that she will never agree with what he just said. Kaori tells him this knowing that Touma was in similar situation as her when they first met, as if it was punishment on herself. Unmoved, Acqua of the Back says that to be angry over something that small is immature, and mocks their beliefs being put in the battlefields where there are no rules. Kaori tells him that it just his reasoning, though he replies that they are walking into his battlefield, and wonders what master pulled Touma up like Kaori had pulled the Amakusa. Hearing enough and with no warning at all, Kaori sped towards him and tried to cut him down with her blade. An angry Kaori shouts at Acqua of the Back, saying that if he knew all that then why he treated him as someone who got involved, asking him why he used the full power of a Saint to attack him, knowing full well that she too had hurt Touma the same way. However, he remained calm, and basically tells that he is confident in what he is doing is in the right and that he needs no excuses for the path he has chosen. As Saints collide, the blood markings on the mace activated, forcing Kaori to increase the distance between them. Acqua of the Back then says to her to show him her belief not via shallow words but by her blade. There, the weight and pressure exerted by the mace exponentially, and the two Saints once again clashed.

Using all of the water available in the 4th level of School District 22, Acqua of the Back creates a complex magic circle made of water that allows him to barrage Kaori with attack after attack of water shaped by magic of many forms, from ice spears to water whips. Moreover, he himself attacked Kaori. However, Kaori persists using her wires to cut them down and make barriers, even after Acqua of the Back predicted that she would be too slow to dodge and block. As their clash continue, Kaori notices that Acqua of the Back is using Divine Mother's Mercy. As they continue doing battle, Kaori grits her teeth though not just because of the pain, but because of Acqua of the Back's blatant misuse of the Divine Mother's Mercy in acts of violence. As they continue to clash, Acqua of the Back states that he is impressed by her managing to endure the great magic circle that spread out to two kilometers in diameter, though asks if her body is at its limit. This surprises Kaori, though she once again had her weapon clashed with his, though she is reaching her limit, what's more, her technique, the Yuisen, is not suited for long-term combat, and that it should only be used when a kill was guaranteed. With Acqua of the Back, a one-hit kill is impossible. In contrast to Kaori's obvious signs of wear, Acqua of the Back remains smiling. Kaori recalls her battle with Misha Kreutzev, and in contrast to her, Kaori feels that Acqua of the Back seems to have an even greater power coming from him. Believing this, Kaori deems that Acqua of the Back should have destroyed himself with that overwhelming power coming from him. Then as she ponders this, Acqua of the Back once again to attack with his mace. Kaori has her sword meet with it, but so great was the power that the ground that she stood on shattered as she endured the attack.

Kaori tries to attack with her sword but Acqua of the Back easily blocks it. Having enough of the battle, Acqua of the Back comments on though fighting another Saint is excellent sport as he hasn't done so for three years, he still has work to do and he doesn't have the time. Before Kaori could respond, Acqua of the Back jumped up into the air with the moon of 4th level's artificial sky behind him. Kaori, being too damaged by their battle is unable to close the distance and is helpless against what Acqua of the Back is about to do. He then recites an incantation of the Divine Mother and the artificial moon behind him begins to glow, and the screen that creates the artificial sky begins breaking apart. After finishing the incantation, Acqua of the Back explosively dives from the screen, destroying the entire artificial sky in the process, and dropped down towards Kaori in order to crush her with the mace. So great was the release of power that everything within a 100 meter radius of the 4th level of School District 22 collapse and fell down to the 5th level. However, as the dust settles, Kaori has endured Acqua of the Back's hit with her sword, though the ground below her feet did not, and she has fallen down. Moreover, the impact was still strong enough to thoroughly damage her.

There in the 5th level, lying on top of debris, she once again stands up, enraged at Acqua of the Back, though relieved that there were no bystanders around. She lifts herself up again and picks up her fallen sword. Meanwhile, Acqua of the Back who is unscathed, asks her where the Imagine Breakers is, wondering if he destroys every level he may be able to find him. This does not sit well for Kaori, and screams his name. Filled with wrath, the injured Kaori grips her sword tightly and speeds towards him. There, their techniques once again clash, with Kaori swinging her sword on him and moving her wires to create magic circles that can discharge fire or ice spells, while Acqua of the Back merely blocks her sword with his mace and maintained a steady barrage of attacks. He absorbs the moonlight on the screen an attribute of the Power of God, the archangel he is aligned to, to increase his attack power. Moreover, he uses the Divine Mother's Mercy to allow him to surpass the limits of God's Right Seat on not being able to use ordinary magic.

In spite of her attacks, Kaori is clearly outmatched by Acqua of the Back, and her injuries bring her no relief, as she had reached her limit, and all her trump cards have been played in the protracted battle between Saints. In this dark hour, however, Kaori can only recall Touma's words back when she herself mercilessly beat him and where he continued to defy her, telling what she was hiding from herself, and that is she gained power because there was something she wanted to protect. She recalls how the powerless Touma stood up against someone whom he possibly could not defeat in order to protect Itsuwa, and believes that it would never lose to those who thought they were "God-chosen" and acted above others. And so, Kaori continued to battle, as she is fueled with the desire in not letting Acqua of the Back get away from her unscathed.

As the battle continues, Kaori is at her limit, and is slowly falling back, and her strength wavering. As Kaori looks on, Acqua of the Back continues to look down on her and the Amakusa Christians. There is just too much of a difference between her and the pure talent and genius of Acqua of the Back. He points out that he will crush them for they chose to fight him regardless if they are incapable of fighting back, to which Acqua of the Back just looks down upon them. Kaori steps inside the shoes of Acqua of the Back and discovers that they are not that different. She is a Saint, and though she cared for her comrades, she looked down upon them, never letting stand beside her in the battlefield, trying to control everyone so that they would not get hurt. With that Kaori realizes her own foolishness and her own weaknesses. Here, she discovers that she still had the power to challenge Acqua all along.

Upon the 4th level the Amakusa Christians heard her call from below; Kaori calls out to her comrades to lend her their power. And their bodies trembled in their place, and those who have lost their weapons in their frailty pick them up once more, for their leader has come 'a calling. They were now recognized by their Priestess, they are no longer a burden to her. Now gathered, Saiji gives his last instructions as the Subsitute Supreme Pontiff, their Priestess, to where the Amakusa should go.

They gather around their Priestess with a jubilant shout, surprising Acqua of the Back. He tells her if he is willing to have the weak help her to save her own life. However, Kaori reveals that she was the weak one, for not believing in her Church's abilities and strengths. Because of these insecurities in wanting to protect what she deemed weak she made mistakes allowed holes in their formations and putting her comrades in danger. And that is why she called her Church back to her, for she can trust herself to them, to utilize their ability to the maximum. Acqua of the Back however, is unperturbed, and Kaori meets her rod with her sword, however, this time the Amakusa Christians cast defensive spells to reduce its impact. As their battle goes on, Kaori points out that Acqua of the Back's strengths are also his weakness. The reason why he can indiscriminately use his Saint powers without his body overloading is because of his Divine Mother's Worship. However, this make his weakness be the Saint Destroyer, as proven by the fact that that was the only time he used a magical defense. Kaori says that to regular Saints, it will only cause them to be unable to move for several seconds, but for someone like Acqua of the Back who has the attributes of the Son of God and the Divine Mother, he will surely self-destruct. The Saint Destroyer forcefully destabilizes the balance that Divine Mother's Worship gives that allows Acqua of the Back to use his Saint powers beyond normal Saints, that is how he can be beaten. Acqua of the Back smiles at this revelation, continuing his assault on Kaori. She strikes at the buildings with her wires around Acqua of the Back, and there he discovers that she has formed from the rubble, a crown of thorns, an iron picket, and a large cross, the method of execution of the Son of God, the weakness that all Saints inherit. Acqua of the Back begins to waver, for surely, though to an ordinary Saint, this method won't do much effect, to someone like Acqua of the Back it spells out his execution. Itsuwa comes close again with her spear, symbolizing the Spear of Longinus that pierced the Son of God. However, Acqua of the Back isn't numbered yet. Impressed by their feat, he jumps again and uses the artificial moon of School District 22 to symbolize the attribute he is aligned to. He falls back the earth with his rod aiming at them, exuding a tremendous magical power. In danger, Kaori prepares to defend against Acqua of the Back, collecting all the symbols throughout history, forming this spell at the last second, turning Kanzaki Kaori into a shield.

Acqua of the Back strikes down, but to everyone surprise, the place where they're standing remains intact. Acqua of the Back's spell was destroyed by the arrival of Kamijou Touma, holding unto the rod that was fused with magic a moment ago. Touma falls down and seals Acqua of the Back. In his shock, Acqua of the Back could not see Kanzaki Kaori charging towards him, holding his rod and shoulder. With his movements sealed by Kaori, and magic negated by Touma as she tries to shake her off. Itsuwa charges towards with her spear. Acqua of the Back accepts the fate and determines to face it to the end. There, the spear strikes him, piercing his abdomen to the back. Crosses of light appear behind Acqua of the Back, intersecting in the middle, causing Acqua of the Back to fly back due to the impact. They later witness Acqua of the Back being propelled into the artificial lake of the 5th level, and then self-destructing, utterly destroying and boiling the lake into a pillar of steam.

Acqua of the Back survives and is able to make a retreat. He later discovers Fiamma of the Right's plans and tries to return to England to stop it.

British Royal Family Arc
Acqua of the Back secretly makes contact with Vento of the Front, where they discuss the movements of France and England after the Eurotunnel bombing, and on how England asking aid from Academy City and America would affect Europe. She also complains about Fiamma of the Right gaining almost complete control of the Roman Catholic and Russian Orthodox forces and that they no longer have any authority. Vento of the Front tells Acqua of the Back that she will not be joining him in England and instead "shock Fiamma a lot more" indicating her later actions in Russia.

Acqua of the Back later visits one of the members of the Divination Operation Brigade, as he needed a new weapon after his last one was destroyed. The weapons keeper, as thanks for the all the work he has done for them, gives him the Holy Sword Ascalon. He also gives Acqua of the Back his arms, his escutcheon that he commissioned 10 years ago, with the artisan that constructed it still remembering him.

British Halloween
Acqua of the Back is apparently nearby Folkestone, enough for him to be noticed by the Knight Leader, who orders a servant to fetch him if he wanted him killed and the coup that is happening in the United Kingdom to be stopped. Sure enough, Acqua of the Back, charges towards the outskirts of Folkestone only 10 kilometers away from Canterbury Cathedral. He knocks out several knights, destroying the axe that was to be used to cut off Villian’s head, and has princess Villian already in his arms. Everyone is shocked except the Knight Leader who has expected him to come as they face him, carrying his great sword Ascalon. As Villian cries, she berates him for being too slow. As Acqua of the Back carries her in his arms leaping away, Villian starts laughing, casting aside her manners. As Acqua of the Back arrives in his destination, he tells Villian that his Bayard that will take her to a Necessarius hideout who will not abandon her unlike in Canterbury Cathedral. Acqua of the Back says that he will deal with the knights and prevent them from tracking her. Acqua of the Back however is silenced as Villian rants on how she has neither power nor authority and that all she can do is run and hide and that there is no value of her being protected by anyone. She tells him that she has lost hope and since the Knight Leader has betrayed her, William Orwell may do so as well, declaring that she doesn't trust him, basically telling him to abandon her. Without a word, Acqua of the Back merely puts her on his Bayard, surprising her. He then tells her not to worry, saying that even if she doesn't trust him, the reason he is fighting for her remained unshaken. Villian is annoyed because that isn't what she wanted to hear from him, but before she can air her complaints she is taken away by the Bayard.

Acqua of the Back and the Knight Leader, to old friends on different sides, would later meet again in the forests of Folkestone and have a long battle there. Each seemingly an even match for one another until the Knight Leader show off the various effects of his sword Hrunting. This forces Acqua of the Back to use the various attributes of his Ascalon, countering each of their attacks, all the while questioning each other's motives. The Knight Leader would continue to justify himself to Acqua of the Back, while he just scoffs at justifications, saying that his reasons do not need words merely actions. In the end, Acqua of the Back is injured after his attacks prove to be not enough against the Knight Leader, who also has a spell that allows him to defend himself against anything he recognizes as a weapon, the same spell that neutralized Kanzaki Kaori's Yuisen a while ago. Acqua of the Back is forced to use his tricks as a mercenary, deception, something an honorable knight like the Knight Leader merely scoffs at to trick the Knight Leader, and eventually injuring him. The Knight Leader failed to recognize a small clasp on Acqua of the Back's sword used to hold the blade as a weapon, and as such loses against him, ending their long battle.

Acqua of the Back would later find an unconscious Index inside a carriage and would come upon more knights, easily defeating them. Kamijou Touma would later arrive, much to his chagrin, and so does Carissa and her Curtana Original. She later demonstrates the sword's fearsome destructive capability, forcing Acqua of the Back to take Touma and Index and then escape. When Touma comes to, he finds himsefl in an abandoned car with Index with Acqua of the Back close by. Touma is surprised by Acqua of the Back still being alive, to which he points out that he shouldn't be as not only did they not have the intention of killing him but they didn't even check if they truly killed him. He then sighs and states that he was also surprised on how they took him down, but says that he was able to bypass it at the cost of becoming a normal Saint. Touma then questions what happened after the explosion, to which Acqua of the Back says that he saved him, leading to Touma questioning why. Acqua of the Back says that it would be easier to let Touma, the center of the disturbance surrounding the world to die, but says things have changed since they met. Acqua of the Back tells Touma of the true boss after his right hand, Fiamma of the Right, the leader of the alliance between the Roman and Russian churches, and says he is also after Index. He tells that to destroy Fiamma of the Right's plans it would be easier to kill him and Index, but says that he would rather destroy the cause of the disturbance and that two of them are mere accessories. He says that Fiamma of the Right can change his plans even if they are dead or spread meaningless destruction out of desperation. He then says that it is necessary to stop to the dispute happening in the United Kingdom, as it may increase the country's strength and lead to a chance to put a stop to the increase in Roman Catholic influence over Europe, and preventing Fiamma of the Right from carrying out his goal. Touma warns Acqua of the Back that Carissa and his Curtan Original with the knights have already taken control of the United Kingdom, though he is undeterred and remarks that her new order is fragile. With that, Acqua of the Back leaves, remarking he should go for an open attack.

Acqua of the Back is later seen a kilometer away from the Anglican Church forces have gathered for their "last supper", as they prepare to attack Carissa. Here, he is worried of his shouldre despite his usage of healing magic. Knight Leader then contacts him regarding the recent overloading of Curtana Original and the collapsing unity of the knights. Acqua of the Back says that it was the magic specialists of the country that have done the deed and asks why the Knight Leader hasn't returned to his knights yet, though he doesn't answer. Acqua of the Back says he knows that the Knight Leader isn't sure if he should, to which Acqua of the Back states that he should watch first before acting rashly. The Knight Leader asks him what would happen if he chose the side where he will fight him again, to which Acqua of the Back says that it would change nothing as he will simply defeat him again. After checking his Ascalon, Acqua of the Back asks the Knight Leader if he could target the Curtana Original using his Thororm Spell that neutralizes everything that he deems as a weapon. The Knight Leader comments on how everything has an exception, as he made sure that the spell would not be used to harm a member of Royal Family under the fear of lèse majesté. Acqua of the Back references that Knight Leader shouldn't be the one to talk as he tries killing Villian earlier. The Knight Leader points out he used a normal weapon instead of his own for Villian. The Knight Leader then gives Acqua of the Back advice on his upcoming battle, telling him not to underestimate Carissa by thinking there is a trick behind her strength or that you can turn around the situation by finding a weakness in her. Acqua of the Back replies on how what he must do hasn't change, and says that there may be an option of defeating Carissa by taking away Curtana instead of killing her. As the two old friends bid farewell to each other, Acqua of the Back notices that Villian has sensed his presence with the help of Oriana Thomson. Seeing as he has said embarrassing things to her to stabilize her mind after he rescued her, he is however unprepared dealing with her. He quickly packs up and leaves, ignoring the Knight Leader's comments.

After Riméa's communicates en masse the full extent of Carissa's plans and her pleas to save her, Acqua of the Back arrives and slams the antenna used for military transmissions on top of Carissa just as she tries to use several cruise missiles equipped with Bunker Cluster warheads on Buckingham Palace where she and the combined forces of the Anglican Church and the knights have gathered to contend against her will. Although, she dodges the attack, Acqua of the Back's actions ensures that Carissa could no longer carry out any of her orders to the armed forces.

After a bit of bantering, Acqua of the Back and the Knight Leader flank Carissa with their swords. Despite using the dimensional debris against them, Carissa is forced back for the first time. The battle however goes ill for Carissa further as Kanzaki Kaori, the first of the Anglican Church forces to stand up again after the Bunker Cluster attack, comes into the battle as well. With three swords against Carissa, and despite her use of the dimensional debris and her swordsmanship, the battle for her is to evade their attacks as much as she can. Carissa acknowledges her limit despite her sword, to which Kaori says that she believes that not everything can be accomplished with only those who are special. She tells Carissa that they were only able to go all out because there are people supporting them, as such, she tells Carissa, that since she is being aimed at by magicians from all directions she can only continue to focus on possible attacks from her blind spots which limit her options. Carissa agrees that the number of allies can determine the victor in a battle, but then says that it is the reason why she never once thought her victory would lie in that direction. At that moment, Carissa uses dimensional debris not on them but on the group of knights working to treat the Anglicans, knocking them into the air. Immediately afterwards, Carissa creates a dimensional to create another debris. The Knight Leader tries to use stop the debris but is instead hit by one of the Anglicans trying to Carissa in a misfire. As the Knight Leader could no longer hold it because of the attack, the debris still hurtles out of control.

Carissa points out that no matter how large a group is they are still a collection of individuals, and as such connections can be severed between these individuals when their weaknesses or openings can be exploited. Carissa continues to attack the group with her dimensional debris. Acqua of the Back tries clashing swords with Carissa alone without the back-up of either Knight Leader or Kaori that made their assault against her effective in the first place. After a clashing a bit, Acqua is later forced to retreat back as he was bleeding. Carissa once again proclaims her superiority in military affairs after regaining the momentum of the battle. Acqua of the Back and the Knight Leader continue to clash swords with Carissa until Queen Elizard arrives and cuts in between, fighting her daughter on her own. He likely witnesses Elizard using the Union Jack to distribute the power of the Curtana Original to the people of the United Kingdom as well at to ask for their help against Carissa if they wish. It is unknown if he is empowered by Curtana Original. Despite this, Acqua of the Back, the Knight Leader, and Kanzaki Kaori once again join the battle as the people of London arrive and fight Carissa in the battlefield.

When Index is finally able to use Spell Intercept on Curtana Original to drain its excess Telesma, Touma, who also swore to protect Carissa like the rest, realizes that Index's Spell Intercept may be temporary. Deeming that he should try to strike now he calls out to Acqua of the Back for aid in getting to Carissa quickly. After simply yelling out to Acqua of the Back he already knows what Touma's plan is. Touma runs to Acqua of the Back and lands on his Ascalon, at which point he then swings it toward Carissa who was 10 meters away. With a smile on his face, Touma is able to destroy the Curtana Original with the speechless Carissa still holding it up. Afterward, his fist then strikes Carissa's face and sends her flying to the ruins of Buckingham Palace. Thus ends the battle and the coup d’état with her defeat and the destruction of the source and symbol of her power, the Curtana Original.

Acqua of the Back receives word from Vento of the Front that the Russian Orthodox Church has made their move. Seeking to end the conflict, he leaves the country immediately, but not before telling the Knight Leader his parting words for Villian in which he hopes that his escutcheon may one day hang in the space reserved for him in Buckingham Palace. Little did he know that the Knight Leader twisted it to make it look like Acqua of the Back was proposing to Villian.

World War III Arc
In Russia he saves Hamazura Shiage from a privateer attack. Later, he sacrifices himself to reduce Misha Kreutzev's power down to 50% so Accelerator and Kazakiri Hyouka can fight evenly. As he lay dying, Hamazura Shiage came across him and convinced him to not abandon his life, and live on for the people he has saved in times past who follow in his footsteps.

Magic God Othinus Arc
He is first seen with Carissa and the Knight Leader after being temporarily released from the Tower of London for the emergency situation involving GREMLIN. As they prepared to leave to attack Sargasso from a naval port on the northernmost edge of Scotland, they had a brief discussion as to the readiness of the group before setting out in one of their Mobile Fortresses (the Queen Mermaid and the Hotel Ariel) for the alliance's operation. The Knight leader then got the conformation to leave and begin the assault.

On route she receives word that America and Russia will be a little delayed, and though the other two can enter as the second wave of attack, they determined that they will take all glory for themselves. William then asks when Touma will get there, to which Carissa states that he should arrive by the second wave, and notes that due to Academy City's Supersonic Passenger Plane he may arrive before the American and Russian forces. As the island became visible, it is bombed by several Grape Jelly bombs and the Mont Blanc bombs. As the attack took place, William notes on how Carissa's methods never change, and warn her that due to the incident she caused in England, the British Halloween, GREMLIN may had analyzed her methods. Carissa replies that if one removes all the waste and search for the optimal usage of one's weapons, everyone will ultimately arrive at the same place. She states that a military run by a nation needs an attack method that is impossible to avoid even if one knows it is coming. As they begin to land on the island, Carissa isn't optimistic enough to think that the bombing was enough to kill all the members of GREMLIN, but believed that since they still have the physical body of a human, then they can be killed.

Landing on the island, they are informed that there is no need for gas masks for there were no toxic substances detected after the bombing. Thus, they and the British forces begin their search for GREMLIN. Then, they hear a voice up on a wrecked tanker in the island welcoming them and introducing himself as Loki. He comments that "Lady Othinus" gave him the task of protecting the Sargasso of the North Sea with his life. His explanation is cut short however, after he is shot through the throat with an arrow fired via the Robin Hood spell. Loki then fell from the tip of the tanker he was standing on and slammed to the ground. Carissa then ordered all of her men to continue moving forward. He then suddenly rises, explaining that he is just an illusion and the real Loki is nowhere near the area. He further explains that he was suspicious of his teammates and worried about a spy, so he created an artificial sky over the true Sargasso and altered Marian Slingeneyer's notes. Reports from the landed forces state that the teams have found no trace of the magic god or the production of the lance in the island: it is completely empty. Carissa and the others then realize they had indeed been led to a false Sargasso on the other side of the world. The illusion bids them farewell and disappears, just as the place is bombed.

Shifting and Fluctuating World
In the final recreation of the world by Othinus created specifically to break Touma's spirit, known as the Version_Omega world in-text, where several characters from the original world have been "saved" or have not experienced great tragedy, members of the Gods' Right Seat are all alive and well. Touma sees them in the park where Othinus put Touma in after recreating the world. Vento of the Front walked hand in hand with her younger brother, Terra of the Left is alive and is drinking iced coffee under the same parasol as Fiamma of the Right and Acqua of the Back.

VS The World
Surviving the explosion in Sargasso, Princess Carissa, Knight Leader, and William Orwell are mobilized on the Hotel Ariel to go to Denmark following the sudden changing of sides of Kamijou Touma with Magic God Othinus. They are later joined by Kanzaki Kaori. They later knock Touma after his fight with Vasilisa and Sasha Kreutzev, taking him into the mobile fortress. They later prepare to use the Curtana's shard to attack Othinus. As Touma comes to, William tells him not to get up, adding that they don't particularly care about him and that it would be best for him if he simply watched as they bring the situation to an end. He also hears Kaori responding to the Knight Leader's query about bringing him aboard by saying that they don't know what the other GREMLIN members are doing so doing so would prevent the possibility of them meeting with him. She then tells Touma where he is. After hearing of Carissa's intention to use the Curtana's shard against Othinus, Touma slams his fist into the floor, destroying it with the Imagine Breaker and causing them all to fall down to a lower level. Seeing this as a hostile action, the four move to attack him.

To her surprise, Touma moves himself into the path of her attack, such that it would kill him if it connected. Moving to avoid it, Kaori tries to incapacitate him without killing him, realizing that he was using her own trait of not killing against her. However Touma curls himself up, forcing her to jump over him and ends up colliding with the Knight Leader.

Touma once again slams his fist on the mobile fortress, causing them to all fall down again. As they land to safety on the lower levels of fortress, Carissa comments on the queerness of Touma's actions as he can't escape the fortress from 1500 meters. William comments on Touma's plan on using Kaori against them. Both Carissa and Knight Leader find out that Kaori is gone. Carissa comments that they could try searching every room in the fortress and that Touma will be cornered eventually. However, William says they don't have time for that as he already realized Touma's plan, though says that it relies on others too much to call it a proper plan. And that plan is for him to use Kaori's character and trait of saving people to help him survive and escape.

Carissa later uses her Curtana shard to attack them and Othinus from afar, though Kaori later manages to divert the power being relayed to the Curtana's shard and destroy Hotel Ariel. Touma's gamble continues even after Touma left Kaori's side, as she fights Carissa, William, and the Knight Leader on her own. They later listen to the speech by Roberto Katze and Queen Elizard regarding the need to not give in to fear and hatred against Othinus, while Kaori continues to fight the other while coughing up blood from the attacks she had received.

Toaru Majutsu no Index PSP game
Acqua of the Back appears as a playable character in the game, and is only unlockable after finishing Kanzaki Kaori's route in the game. He is the final boss for Kamijou Touma's route, as well as Kanzaki Kaori.

Along with Stiyl Magnus, Acqua of the Back is one of the tallest characters in-game. He carries the sword Ascalon, which allows for great range but at the price of a terribly long set-up. Acqua of the Back's heavy attacks are water-based magic spells, which when activated requires the player to activate it again to be used. This unique feature, allows the player to delay the attack until the right time. This can be exploited, as Acqua of the Back can use all heavy attacks on the character at relatively the same time if timed properly, dealing great damage. Acqua of the Back also has an attack that draws an opponent closer using a purple lighted Ascalon.

Acqua of the Back is notable for having no other expression than a scowl in his 2d sprite during the talking parts of the game.

Abilities
His magic name is Flere210, "The one who changes the reason of tears" (その涙の理由を変える者). Flere is a Latin word that means "tears". The significance of this name suggested that William held his weapon in order to transform cold tears, implied as sadness, to warm ones, implied as tears of joy. Moreover, for a magician to be able to engrave a magic name on their chest, showed that they had overwhelming strength.

As a mercenary, he has many years of battle experience, and coupled with his Saint and powers as a member of God's Right Seat makes for him as a great threat even to the likes of Kanzaki Kaori, a renowned fighter in her own right. Indeed, even after losing both his Saint and God's Right Seat abilities, he is still seen as capable enough to join the operations against GREMLIN alongside Carissa and the Knight Leader.

As he once was a Saint and had Divine Mother's Mercy, the reason why two incompatible elements that resided in his body didn't go run amok was because of William's pure talent. Moreover, even after being depowered twice, the methodology for freely manipulating great still remains within him.

Sainthood
As a Saint, William had Stigma (聖痕 (スティグマ) ), giving him the ability to call upon God's power, endowing him with super-human capabilities. As Saints are still human, they have a limit to using the power created through Idol Theory with their own power. Moreover, if Saints used their power at 100%, the high pressure would cause the Saint's body to self-destruct.

As Acqua of the Back, William had Divine Mother's Mercy, allowing him the nullify the limiter his body imposes on itself as a self-defense instinct, allowing him access to 100% acces to his capabilities as a Saint without consequences. After the events of the World War III, William also loses his powers as a Saint.

God's Right Seat
As Acqua of the Back he is blessed with the nature of the "Power of God," as he is aligned with the Archangel Gabriel after purifying his body from the Original Sin. Normally, this conversation makes him lose his capability to cast human magic but gained the capability to cast angelic magic. However, because of the fact that he Divine Mother's Mercy inherent within him, it blossomed after becoming a member of God's Right Seat, allowing him to bypass the restrictions of this purification and allow him to use normal human magic.

As a result of his alignment with Gabriel, he is associated with the color blue, the moon, and the water. His garb represent this connection, composed mostly of blue, Moreover, he also holds the position of the "back" or "rear" as his name indicates. Prior to losing his Sainthood, his body had the stronges "link" to Gabriel as a member of God's Right Seat.

Divine Mother's Mercy
As a result of his alignment with Gabriel, his latent abilities have blossomed. It is because of Gabriel's relationship with the Divine Mother, the Virgin Mary. As he was the one who informed her of the birth of the Son of God. This allows him to use spells related to the Divine Mother to a certain extent, specifically the Divine Mother's Worship, which leads to him being blessed with Divine Mother's Mercy (聖母の慈悲).

His Divine Mother's Mercy bypasses the restrictions that make it unable for a member of God's Right Seat to use normal human magic. Moreover, as stated above, it removes the limiters on his body, allowing him to use the full extent of his superhuman speed and strength as a Saint. Not only that, this attribute allows him to negate any punishment, making him nigh-invulnerable.

Weakness
Due to his nature being both a Saint and having the attribute of the Divine Mother, he continuously needs to maintain those two powers through his sheer talent to allow them to coexist his body as so they won't go out of control. Because of this, he was especially vulnerable to attacks that represent the things that have harmed the Son of God in his crucifixion. As such, the Saint Destroyer was his one true weakness as it forcefully destroys anyone with a body similar to that of the Son of God and the Divine Mother to self-destruct. Normal Saints who are caught in this attack just make them unable to move for a few seconds. Indeed, even Acqua of the Back was keenly aware of the apparent danger of Saint Destroyer and necessitated in him using a magical defense against it.

After getting hit by a much more potent version of Saint Destroyer, which included not only the spear that represented the Spear of Longinus, but objects such as the cross and the crown of thorns, Acqua of the Back lost his Divine Mother attribute in an explosion of power.

Other spells and magic
Already being able to use water spells ten years prior to the start of the story timeline, being aligned to Gabriel which had power of water is an obvious advantage, greatly increasing the offensive power of his attacks.

Acqua of the Back can use Runic Magic, though seems to specialize in using water runes. He uses it on both the Amakusa Christians as well as Kanzaki Kaori on his own weapon. Using water, he applies a layer between his feet and the ground, allowing him to glide on the floor instead of running, allowing him to move in such a way that he can't be predicted by opponents.

When water is present, which includes water vapor, Acqua of the Back can shape it into any form he desires from water hammers to ice spears. Moreover, he can form a magic circle from the sources of water that is present, as he did in School District 22 on the 4th level, where he used it to barrage Kaori with attack after attack of water spells. One of his most powerful attacks, in conjunction with his Divine Mother's Mercy is to leap high up into the air, with the moon or something else that represent the moon, and use his weapon to crush his enemy. It is powerful enough to make entire steel and concrete structures collapse.

Some of the other spells he is capable of include vacuum cuts, avalanches, as well as pulling his weapon out from his shadow causing an explosive sound.

Mace
Before obtaining Ascalon, Acqua of the Back used a large Mace (メイス) as his only weapon. It was 5 meters long, appeared in shape like an old European knight's lance, and looked like a huge umbrella created from steel that is used to construct a building. The mace is apparently strong enough to withstand the abuse it takes from Acqua of the Back's use of it in his battles.

Ascalon
Great Sword Ascalon (聖剣アスカロン): Acquired by Acqua from the Divination Operation Brigade, which was in debt to him, this giant sword is a spiritual item created by an artist at the end of the 16th century who based it on the legendary sword used by St. George. Ascalon was created around the idea of working out what exactly would be needed to slay the dragon from the legend if it actually existed. It is said that though certain writers described the sword in the legend as a one-handed falchion, when such a weapon was actually constructed, the result was a giant sword 3.5m long and weighing 200kg.

The sword possesses various traits which are designed to allow it to be used in different ways, meant to cut through the different parts of the dragon. Magical power is supplied to the section of Ascalon which is to be used and the shine of the blade changes color depending on which function is being used. Embedded within the giant sword's grip is a hidden, smaller sword, about 1m long. This sword can release its blade on a thin wire connected to the grip, which can be extended and retracted. A small clasp mechanism is located on the grip to secure the blade. A giant mace can also be produced from the wire.

After Acqua lost his power as a Saint and his Divine Mother's Mercy during World War III, he wasn't able to wield Ascalon anymore.

Bayard
Bayard: Acqua has one of these animated metal horses, capable of evading magical detection, in his possession at the time of the coup d'état. He used it to transport Princess Villian to safety while he fought the knights.

Design evolution
Acqua of the Back's preliminary design was drawn after the release of volume 13. Acqua of the Back's design has evolved tremendously. Originally, Acqua of the Back wore blue and had blue hair, and his form was skinnier than the current design he has. Haimura states that he wanted to make Acqua of the Back look like a large man, and is the opposite of Accelerator.

Acqua's design was later finalized around the time of volume 15, giving him brown hair and a change of clothes, and a bulkier form. Haimura states that he wanted to do something different to Acqua from Terra and Vento, and as such added fantastical elements to his design, this is also carried towards Fiamma's design. By volume 17 and 18, Haimura once again redesigned Acqua a little bit to stand out more, giving him a bulkier appearance, and according to his own words, now looks like an old rival and a friend.

Trivia

 * The narrative from Volume 17, chapter 4, part 8 echoes the Volume 17 prologue, suggesting that William Orwell is just like St. George in terms of arriving just in time to save the damsel in distress.
 * Every magical attributes of Acqua of the Back are a symbolic representation of the three most important characters of the : as a Saint, his body and abilities are a replication of the Son of God's; as a member of God's Right Seat, he is aligned with the Archangel Gabriel, the angel of the ; and he possesses the Divine Mother's Mercy, a reference to the Virgin Mary.

Quotes

 * (To Touma, from Index Volume 13) "I am a Saint. Pick any unreasonable fight with me and I will shorten your life span."
 * (To Terra of the Left, from Index Volume 14) "Just so you know, there is no way you will be chosen by God. I never thought you would remain deluded at this stage. Do you really think you belong anywhere but hell? God knows all. You can ask him for the details at the Final Judgment."
 * (To Villian after saving her, from Index Volume 17): "Are you alright, princess of this country?"
 * (To Villian, from Index Volume 18): "Do not worry... Even if you do not trust me, my reason for fighting for you remains unshaken."
 * (To Knight Leader, ibid): "I do not need decorative words to speak to others...The reason I fight is expressed with my body and my sword!!"
 * (To Knight Leader right after defeating him, ibid): "I'm sorry to say that, I didn't bring a suitable blade for cutting an old friend."
 * (To Knight Leader, ibid): "No matter who the enemy may be, what I must do does not change."
 * (Regarding Touma from NT volume 8): “When will that right arm boy get here?”