Tatemiya Saiji

Tatemiya Saiji (建宮斎字) is a character introduced in Toaru Majutsu no Index. He is the Substitute Supreme Pontiff of the Japanese-based Amakusa-Style Remix of Church, leading the sect on behalf of Kanzaki Kaori who has vacated the position of Supreme Pontiff before the start of the series. As Substitute Pontiff he and the Amakusa Christians went on missions that carried the ideals that their Priestess (Kanzaki) believed in, and that is to always aid those in need. He later willingly steps down from the position after Kanzaki Kaori returns as the Supreme Pontiff of the Amakusa Church. An amicable man, he has to lead his group several times to aid Kamijou Touma and is a reliable ally to him in dire times.

Appearance
Saiji is described as being around 25 years old with a tall and skinny figure. He wears very loose clothes, an over-sized shirt with a slanted red cross emblazoned upon it. His hair is pitch black and is implied that he used hair dye on it, and is described as something akin to a carapace of a beetle. As with its style, it is like Touma, except messier. He wears basketball shoes with 1 meter long shoelaces. He also wears a rope hanging around his neck, where four to five mini-fans about 10 centimeters big are hanged.

As being part of Amakusa, all of what Saiji wears is part of his magic and is deliberate. With the St. George's Cross he wears it to signify that he wants to join with Kanzaki Kaori, their Priestess, with the Anglican Church.

Personality
To allies he is an amiable fellow who has shown to care deeply for his comrades, preferring to attack the Agnese Forces alone to free his comrades rather than escape without them. Moreover, he gets enraged when someone hurts them, as shown when Touma reveals that he has defeated Uragami. In pursuits of their interests, Saiji will gladly aid them, as shown when he and the others try to help Itsuwa become closer to Touma, and even shooed away the Knight Leader's advances on Kanzaki. He has shown distaste for them feeling sorry for themselves and being in unease, as shown when he forced Itsuwa to pay her debt with Touma saving her from Acqua of the Back, as well as aiding Itsuwa to get a hold of herself after discovering Touma being alive after believing he was dead after World War III.

As the substitute leader of the Amakusa Church, he closely follows the tenets set down by Kanzaki Kaori, specifically, to reach out to all those that are abandoned. When battling, he is shown to be boastful and confident. He often makes swaggers and sarcastic comments during them, but that does not entail that he is not serious, as shown during the Battle of the Church of Orsola.

Background
Although older than Kanzaki the Priestess, he truly believes in her capability of leading the Amakusa Church. He may have been present during several key events in Kanzaki's life that lead her into defecting from the Church three years prior to the start of the series. After her defection, Tatemiya Saiji became the Substitute Supreme Pontiff. Because of her defection, the Amakusa blamed themselves for their weakness, and tried to become stronger, taking into mind the teachings of their Priestess, and specifically, to reach out to all the abandoned.

By the time of their introduction into the timeline, they are well known enough for even people like Orsola Aquinas to seek refuge. However, the Church still wanted to join Kanzaki, as is the reason why Saiji wears St. George’s Cross on his shirt, to show that they want to join her. He may have also been present during the creation of the Saint Killer spell, in an attempt to truly know of the strengths and weaknesses of Kanzaki in order for them to stand by her side.

Orsola Aquinas Rescue Arc
Saiji and the rest of the Amakusa Christians were on the pursuit of a woman named Orsola Aquinas of the Roman Catholic Church. Stiyl Magnus, a representative of the Anglican Church, suspected that Saiji and his group have kidnapped Orsola Aquinas and the Book of the Law to achieve ultimate power. However, the truth was that they were trying to help her escape, but she could not trust them as they were melee fighters who carried weapons. The Amakusas continued on their pursuit of her and eventually recaptured her in an encounter with Stiyl Magnus, Index, and Kamijou Touma, who represent the Anglican Church, and the Agnese Forces led by Agnese Sanctis on a neighborhood just outside Academy City gates. In order to escape their pursuits, Saiji utilized a magical portal located on the nearby Parallel Sweets Park and waited for the exact time they could use the portal to teleport away from the scene. However, the Amakusas' location was spotted by the two forces. Saiji confronts Touma and Stiyl who puts up a good fight as well as avoiding everyone's attack. But he is defeated by Touma and Stiyl who ram into him and binding him through Stiyl's runes. While in custody he has a chance to talk to Touma and Index, trying to convince them that they are not the enemies, rather, the Roman Catholics were as they wanted to kill Orsola Aquinas, and that they did not want to disappoint Kanzaki again after all the people who sacrificed themselves for her sake. Touma and Index then hear the distressful cry from Orsola and suspect something strange about the situation. Then Lucia and Angelene appear to take him in for judgment. But Touma sakes for the truth and accidentally touches Lucia who becomes hostile and tries to kill him. Saiji attempts to move but is magically bound and cannot. Index helps Touma out of his situation and the two nuns retreat.

After freeing him, Touma, Stiyl, Index, and Saiji, discuss on what do now, seeing as Orsola Aquinas has been captured by the Roman Catholics. Stiyl plainly says that she will be taken to the Vatican to be judged guilty and then executed, frustrating Touma as he and the Anglicans cannot meddle in the internal affairs of a different sect. Saiji tells Touma and the others that he will be fine on his own, saying that he will free his comrades and Orsola. He later does free his comrades held in another part of the Church of Orsola, and later comes in at the knick of time to aid Touma, Index, and Stiyl who came to rescue Orsola, having discussed their plan to save Orsola before Touma intervenes. As the fight draws out, he witnesses Index's Sheol Fear, as well as the horrible things that Roman Catholics would do to go against it. Due to the overwhelming numbers of the Roman Catholics, Saiji, Stiyl, and Index go to a chapel where Touma and Orsola hold themselves in as they discuss their strategy. He later discovers that Orsola's decipher method of the Book of the Law was a false one and laments in a joking manner that they can't use that information against the now rabid Roman Catholics of the Agnese Forces. As the chapel doors are torn down by the battle nuns, he and the others are forced to retreat.

He later has his comrades place Stiyl's rune cards all over the Church of Orsola grounds to create a large magic circle so Stiyl can summon Innocentius. It was part of Touma's plan and he later discovers the nuns being cowed by Innocentius as well as their leader being cornered. Saiji later witnesses Agnese Sanctis' defeat at the hands of Kamijou Touma.

As part of Laura Stuart's plan to tether Kanzaki Kaori's loyalty, she allows the Amakusa Christians to join the Anglican Church. Saiji and the rest then began living in London's Japantown.

La Regina del Mare Adriatico Arc
After the integration of the Amakusa Christians and Orsola Aquinas into the Anglican Church, they decided to help out with Orsola's move from her house in Chioggia in Venice to England to the church's dormitories there. During this time, Index and Touma, who are on vacation, end up in Orsola's doorstep as well. During the packing of Orsola's belongings, Saiji and the others began their plan of moving Itsuwa and Touma closer together by suggesting her to give hot hand towels to him.

That night, the Amakusa receives a distress call from Index, who is separated from Touma and Orsola during an ambush attack from the Roman Catholic Church and the summoning of the Queen's Fleet, which made reaching the two a difficult task. In the rescue mission, the Amakusa stealthily close in on the Queen's Fleet by using wooden submersibles, which they later use in retrieving Touma, Orsola, and sisters Angelene and Lucia, who are captives of the Queen's Fleet from a brutal bombardment in the middle of the freezing waters of the Adriatic Sea.

Saiji, after preparing a feast for his men and his newest allies, prepares a counterattack, this time to rescue Agnese Sanctis who, along with the entire Agnese Forces, are held captive following their failure to exterminate Orsola Aquinas. Using shock and awe tactics through Fire Ships, he infiltrated the Queen's Fleet with the entire force of the Amakusa Christians while Touma, Orsola, and Index locate Agnese's location.

After a tense battle between Touma, Orsola, and the Queen's Fleet's commander Bishop Biagio Busoni on one side of the battlefield and between the Amakusa and the Agnese Forces on the other, the entire Queen's Fleet is sunk. The Agnese Forces, their leader Agnese, Touma, Index, Orsola, and the Amakusas leave the battlefield with minimal injuries, and Biagio Busoni is surrendered to the Anglican Church.

Anglican Church–Russian Orthodox Church Prewar Conference
Orsola Aquinas mentions that Tatemiya Saiji met the Knight Leader in Japantown, wanting to invite Kanzaki to a dance. She states that Saiji shooed Knight Leader away telling that there is someone in Academy City that Kanzaki loves and that she prefers to lead younger men than to be led by someone older than her. Kanzaki does not take the rumors spread by Saiji well.

Document of Constantine Arc
Itsuwa states that the 52 combat-ready Amakusa Christians, including Saiji, are the ley lines and other magical properties of the land in France on a request from the Anglican Church.

Acqua of the Back Arc
Two days before the start of the arc, the Anglican Church and Academy City both receive letters from Acqua of the Back threatening that he will crush Touma, and warns them that if they intend to stop him, then they must prepare to use all their power. Moreover, he sends the corpse of Terra of the Left to the Anglican Church to prove the letters' authenticity. Because of this threat, the Amakusa Christians were sent to protect Touma, since they can be used as a scapegoat when things get bad and that since they're based on Japan it gives them a geographical advantage.

Saiji first comes in with the rest of the Amakusa, observing Itsuwa's progress with Touma, though he is disappointed by Itsuwa's pace. After arguing about Itsuwa's hidden breast as well as Tsushima's beautiful legs, he takes a soccer ball and kicks it towards Touma's head in order for his face to land on Itsuwa's breast. He is successful, but he manages to catch the attention of Misaka Mikoto, irate on what had happened to Touma. Saiji and the other later leave quickly without a trace.

The group later comes into School District 22, scattered to have Touma be the center, and continuing their protection of Touma from far away. Ushibuka later comes up to him and asks if Acqua of the Back really is going to attack, to which Saiji offers his observation to him. Here, Saiji confirms that Touma is worth protecting not because he is their savior, but because he is also their comrade as well. Then Saiji wonders about the value of Kamijou Touma to Academy City, to the Anglican Church, and to God's Right Seat, to which Saiji concludes that there is a lot of hidden information regarding Touma. However, Saiji suddenly feels constricted and discovers that he and their comrades are the only ones who are walking in the street. He 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. They are later bruised and battered but not that much worse than Touma who has been hospitalized. After hearing the doctor's diagnosis in a hospital in School District 22, Saiji says that they should at least apologize to him, but the doctor vetoes the thought. Powerless, the Amakusa can only regret that they have failed to protect Touma. Saiji sees Itsuwa sitting in the corner sulking and dwelling on her own failure of protecting Touma, to which an irritated Saiji raised her and told her on how Touma could've protected a woman such as her. Before Itsuwa could raise her hand on him in anger, Saiji throws her down and tells that Acqua of the Back will come back and asks if they should continue sulking or stand up and confront Acqua of the Back and defend Touma. He tells Itsuwa that if she wants to apologize to Touma, she must make it so that she is someone who was worth protected by him. He asks his comrades if there is anyone who feels the same way as Itsuwa before as so he could wake them up. Predictably, no one responds, and they once again prepare to take on Acqua of the Back. They later have the 50-strong Amakusa Christians in an alleyway in School District 22, awaiting the intelligence from the Anglican Church regarding Acqua of the Back. Saiji reports to his comrades that Acqua of the Back is currently fighting unmanned robots and that they should prepare first before challenging him. As the Amakusa prepares for their battle against Acqua of the Back, Saiji turns to find Itsuwa, finding out that she is intensively strengthening her weapon beyond normal. This makes both Saiji and Ushibuka both unnerved, with the former thinking that he went overboard with her. Orsola Aquinas later calls Saiji to inform him of what they learned of Acqua of the Back, and though they learn no weakness and discover that Acqua of the Back is more powerful than they thought, Saiji and the others are still determined to protect Touma from him.

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 space between the third and fourth level, a hydroelectric turbine power plant. Saiji and the other 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 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, Ituswa 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 her master and leaves, for Kanzaki Kaori has arrived to challenge him. The Amakusa Christians watch from the distance as Acqua of the Back continues to dominate Kanzaki and the battle falling down into the 5th level of School District 22. Right now, they are powerless, and the injuries and battering they've incurred from Acqua of the Back playing with them have left some of them to lose their grip on their weapons. Moreover, because Kanzaki is protecting them, it seems that their efforts have come to not, for once again their Priestess stands in front of them to protect and not them standing beside her to aid her. The Amakusa sink into despair as the battle between the Saints continues.

Kanzaki is at her limit and is slowly falling back, and her strength wavering. As Kanzaki 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. Kanzaki 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 on the battlefield, trying to control everyone so that they would not get hurt. With that Kanzaki 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; Kanzaki 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 Substitute 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, Kanzaki 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 mad 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 Kanzaki meets her rod with her sword, however, this time the Amakusa Christians cast defensive spells to reduce its impact. As their battle goes on, Kanzaki points out that Acqua of the Back's strengths is 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 makes his weakness be the Saint Killer, as proven by the fact that that was the only time he used a magical defense. Kanzaki 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 Killer forcefully destabilizes the balance that Divine Mother's Worship gives that allows Acqua of the Back to using 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 Kanzaki. 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 sure, though to an ordinary Saint, this method won't do many effects, 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, Kanzaki 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's 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 Kanzaki, and magic negated by Touma as she tries to shake her off. Itsuwa charges towards with her spear. Acqua of the Back accepts 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. They later discover that Acqua of the Back is still alive and retreated after being defeated.

British Royal Family Arc
Saiji is with the other men in the break room of the apartment the Amakusa Christians are staying on, they overheard Itsuwa hesitating to buy the Great Elemental Fairy maid outfit, much to their dismay, and discuss plans on how to push Itsuwa further. Later, when Itsuwa becomes drunk after a drinking binge after seeing that Touma did not arrive in London as scheduled, Saiji and Isahaya planned to ruse Itsuwa in thinking Touma would arrive at their apartment. Upon hearing Isahaya's false report, Itsuwa is bebothered and flustered, however, after she discovers that the "Spiky-haired" person Isahaya was talking about was Saiji, she knocks him over with the tea table in anger.

The Amakusa Christians later intercept Bayloupe of New Light near the entrance of a subway station. Bayloupe is surprised, to which Itsuwa says that the Amakusa Christians are proficient in blending in with the environment, which allows them to detect people who do not belong. Itsuwa tells her that she will be taken to the Tower of London, but she refuses, there she puts on her special horns and prepares to leave with her case that supposedly contains a spiritual item. Itsuwa responds and strikes as Bayloupe, however, she meets it with her own polearm. As they clash, the other Amakusa Christians take out their hidden weapons, seeing this, Bayloupe smashed the wall she was leaning on previously, intending to flee. Itsuwa tells Saiji and the others to guard the entrances and exits and proceeds to fire a gun with blanks in the underground area, forcing the people to quickly leave as Itsuwa makes her pursuit. After Itsuwa traps and defeats Bayloupe in one of Necessarius' labyrinthine halls, she later regroups with Kanzaki and the rest of the Amakusa Christians after discovering the truth about the case they were carrying with the help of Sherry Cromwell.

British Halloween
As the British Halloween begins and Princess Carissa shows her true colors, the Amakusa Christians hijack the seaplane moored on the lake on Hyde Park after evacuating the Necessarius Women's Dormitory, as the Knights of England under Carissa, has shut down all air transportation. The plane is later spotted by Carissa and Knight Leader, and later has Kanzaki Kaori drop upon them to confront them directly and the coup. The Amakusa Christians later arrive at Folkestone and sent scouts to search for Touma, Floris, and Princess Villian. Moreover, they also retrieve their Priestess Kanzaki after her defeat at the hands of Knight Leader and began to prepare for a defensive battle. One of the Amakusa Christians suggest breaking formation in order to aid Touma in searching for Index, but he declines and states that the best move is to have Kanzaki back in shape and protect Villian with all their combatants. Despite their insistence, the Amakusa Christians reluctantly accept.

After the now normal Saint Acqua of the Back saved Kamijou Touma and Index from Carissa, Touma and Index later meet up with the Amakusa in the forest of Folkestone. The Amakusa Christians have heard of the explosion caused by Carissa in the battle earlier and had come to investigate without being detected. They later go into the seaplane they used, crammed with the other members of the Amakusa Church. Tatemiya Saiji reports to Touma that Carissa is heading for Buckingham Palace, while the other Amakusa Christians keep egging Itsuwa on. Continuing with his report, Saiji states that to stop the coup, they have to stop Carissa, and states that unlike their Priestess, who was born with her power, Carissa only has the Curtana Original, which if they can destroy, would rob her of her power. Touma later sees Kanzaki, whom upon seeing his gaze, reports that the Agnese Forces and Sherry Cromwell are currently in battle, and states that she is still recovering before she can go back to fighting form. Touma then asks if she is all right, to which she says that she wishes that she can tell that it wasn't a problem. She smiles and looks at Saiji who simply nods. Saiji then speaks about Acqua of the Back's involvement and states that it may be in their favor. Touma, however, doubts his allegiance and says that he doesn't even know if truly did defeat the Knight Leader. Saiji replies that he has scouts that determined that Acqua of the Back had fought the Knight Leader, and since the former is moving about, it can be assumed for now that the Knight Leader has been defeated. This means that the only one standing in the way is the troublesome Carissa.

Kanzaki then asks what happened to Queen Elizard and Archbishop Laura Stuart, to which Saiji states that he hasn't received reports regarding them, and that, according to the Knight's communications network, the two of them at least attempted to escape while being transported from Windsor Castle to London, at which point they have no idea what had happened afterward. Touma asks if Elizard has something up her sleeve that can end the crisis in one shot. Saiji replies that they can hope for her having a kind of direct battle ability, but even if she does not have a plan, her mere existence is very valuable both in domestic affairs and in diplomatic affairs, as such, the real way to defeat Carissa's new order, in the end, may lie in her. Saiji then restates the importance of preventing Carissa from using the Curtana Original. Touma doubts that they can enter the now occupied London and get to Buckingham Palace, but Saiji states that they can at least sneak into it. Saiji states that there is the Victoria subway line that runs directly beneath Buckingham Palace. Saiji quizzes Touma on why Carissa would go back to Buckingham Palace. After giving the usual responses, Saiji explains that the reason is because of Curtana Original, which has too much power, as such Carissa needs a large facility to suppress its power if it goes out of control. The facility in question is built within the Palace where the Curtana Second is supposed to stay for the majority of the year. Curtana Original was lost in history after going out to control, as such it is likely they have planned on a way of preventing Curtana Original from going out of control. Kanzaki later adds that they have a theory that the large facility in Buckingham suppresses Curtana Original's power by reversing the flow of the magic power. Since Carissa has entered Buckingham Palace to suppress its power, Kanzaki states that now they have a real chance of making it go out of control, rendering it unusable.

Continuing with Kanzaki, she states that the knight's connection with Carissa is not as strong, as they are being led by her instead of their leader. Kanzaki says that the knights joined in with the coup d'état with her as they deemed that it was the most beneficial path for England. Moreover, they will turn their backs on her the moment they determine that continuing to follow her would be disadvantageous for England. This implies that whether or not she can use Curtana Original is directly linked to the success or failure of the coup d'état. Touma then questions on how Buckingham Palace having the suppressor to Curtana Original if they said that it didn't have magical devices, to which Kanzaki says that there are no magical devices in Buckingham Palace during times of peace, but a subway line runs beneath the palace. A special railroad car with a magic circle on it is kept in an area branching off from the normal track. The special car is set up so it can be promptly taken to the area directly below Buckingham Palace when Curtana Original is headed out of control. Kanzaki states that the Anglican Church's plan is via using the air fortress Coven Compass to use a large amount of magic power to forcibly interfere with Curtana Original via the subway in an attempt to send it out of control. Kanzaki states that Coven Compass is 500 kilometers away from Buckingham Palace, as such, Church members are setting up relay points to guide the magic power. Touma concludes that they are heading to London to confront Carissa after Curtana Original has been sealed, but Kanzaki is hesitant to say. Saiji then tells Touma that because the special railroad car used to bring Curtana back under control is kept in an area branching off from the normal track, the part where it branches is protected by a magic barrier. This necessitates with them needing to destroy the barrier, to which Touma concludes that they will need to go into a subway station near Buckingham Palace and destroy the barrier with his right hand. However, Saiji states that there is a security measure put up on London which allows the Knights of England to detect them in a map. In conclusion, people who can refine their own magic power cannot take part in the plan. Moreover, without a member of the royal family like Princess Villian, they cannot interfere with the magical barrier within the subway tunnel or the special railway car with the magic circle. In the end, the mission to enter the subway lies at the hands of Touma, Index, and Villian.

After the successful mission of Touma and company, Saiji watches the magical explosion of Curtana Original going out of control in Buckingham Palace with a pair of binoculars. It was a calm before the storm, and the members of the Anglican Church, including the Amakusa Christians and the Agnese Forces, have gathered in the verdant outskirts of London. Saiji mentions that they succeeded in weakening Curtana Original but they were still affected by its reaction. Ushibuka then states that it is because of the telesma emitted in all directions with the second princess at the center, affecting the spiritual items and facilities within London, and destroying three small churches in the process. Kouyagi adds that the Telesma in London is incredibly dense, so much so that using magic within London would envelop the city in an explosion. Saiji agrees, stating that they could mentally take down the knights now that Carissa has been weakened further. Isahaya comments that they need to wait for the Telesma in London to diffuse before they could attack, though he worries that the Curtana Original might be restored and the Knights of England would focus on defending Buckingham Palace in the meantime. Saiji states that though he is unsure of the knights, the Curtana Original is too strong and cannot be restored easily without leading into a catastrophe if it fails. With that, Saiji concludes that they have a little break, though states that it is also a preparatory period before the final battle. Tsushima retorts that they should do their jobs properly then, to which Saiji and other males of the Amakusa begin arguing back against her. However, Tsushima is unperturbed as she sees them looking at Itsuwa and her apron using the binoculars. During the calm before the storm, the Amakusa and the rest eat to restore the stamina they lost from the fleeing and battling. While Itsuwa is flustered on what she should do with getting close to Touma, Saiji appears having apparently gotten the Great Spirit Revealing Maid outfit. Saiji reveals that the designer was from London, as such he picked one up just after the coup d'état started, to which Itsuwa just freaks out. Seeing this, Kanzaki lets out a sigh of relief, believing that her own maid outfit was lost back in the ensuing chaos of evacuating the Necessarius Women's Dormitory. But Saiji reveals that he also picked up both the Fallen Angel Maid and the Fallen Angel Ero Maid from the dormitory, much to Kanzaki's befuddlement. The Amakusa men then started talking about Kanzaki having other more erotic maid outfits, infuriating her even more. This was apparently because they have never seen their Priestess in a Fallen Angel Ero Maid outfit. All the discussion about maid outfits reached the ears of the Agnese Forces and even Sherry Cromwell and Orsola Aquinas.

They arrive in London, groups splitting up between 20 trucks heading for Buckingham Palace. The Amakusa Christians have prepared spells against the checkpoints, but have discovered that the city has none of it, to which Kanzaki assumes that the knights' forces are concentrated in Buckingham Palace. Kanzaki plans to use Touma as a powerful but slow-moving mobile cannon, where she and the Amakusa Christians will bait Carissa towards Touma's direction in order for him to destroy Curtana Original. The operation starts with Coven Compass and Selkie Aquarium's long-ranged magical bombardment of Buckingham Palace, which would allow them to get close to the Palace as Carissa will be too busy defending against them. Complicating matters even more, Carissa summons her own fleet of mobile fortresses, Griffin Sky. As Kanzaki Kaori arrives to do battle with Carissa after saving Touma and Princess Villian, the Amakusa Christians, the Agnese Forces, and other members of the Anglican Church arrive, such as Orsola Aquinas and Sherry Cromwell with her Golem. All of them arrive in shock at the level of battle Carissa and Kanzaki were fighting on, however, they later realize where they were in and try to either assist Kanzaki or attack Carissa. However, despite the number of advantages, they are unable to take down Carissa. The Griffin Sky mobile fortresses however arrive as her reinforcements, and rain lances upon Sherry's golem, raining debris threatening to crush the rest of the forces, while Agnese and Lucia frantically try to take cover. Seeing how the Griffin Sky could thin their numbers, Kanzaki orders the Amakusa Christians to split into teams to deal with Carissa and the Griffin Sky mobile fortress. The Amakusa Christians quickly do as their told, and though one of which was not taken down, Kanzaki was able to use it to her advantage. Swinging the lance it had to hit the other Griffin Sky mobile fortresses and attack Carissa. Itsuwa later encourages to make teams in order to increase their attacks on the Griffin Skies, to which the Amakusa Christians do so quickly.

Saiji and Itsuwa, close-quarters fighters, are struck down by a projectile attack by Carissa. After Villian catches Carissa off her guard by showing off some unexpected magic through the use of her bow gun and the magic power Cover Compass was bombarding, Carissa tries to strike down Villian. However, before she is able to, Saiji, Itsuwa, and the other Amakusa Christians take her away to face Carissa themselves. They were faster than before thanks to Villian's spell that Carissa thought was meant against her. Carissa tries to desperately to remove the cores falling down to support the close quarters' fighters, however, when she has a swing, her Curtana Original doesn't cut a dimension as it is negated by Touma before she is able to do so. Villian once again fires her bow gun, and Carissa tries to defend herself, however, it was all but a ruse to allow Index to alter the trajectory of the Coven Compass' attack spell towards her, hitting her.

However, Carissa is not felled by the attack due to the Curtana Original, though there are a few scratches on her body. With Griffin Skies wiped out, Carissa calls for a bunker cluster missile to be fire on Buckingham Palace. Running out of time, Kanzaki sets up a defense barrier in the air with a range of 3 kilometers in every direction to intercept them. However, as Kanzaki was busy she is totally defenseless, Carissa strikes her but she manages to evade. However, the construction of the defensive spell was interrupted and Kanzaki starts over again, but she did not make it in time. Explosions then rang out, but despite this, the defensive spell was successful in defending London, and only a few managed to hit through the gaps of her spell. Touma later calls out to Saiji among others after the bombs fell but there were no responses. After Princess Riméa's broadcast revealing Carissa's intention in the coup d'état, the Knights of England later appear in the battlefield, some of them heal the members of the Anglican Church. It can be assumed that some of the members of the Amakusa participated in attacking Carissa with their spells during her clash with Kanzaki, Acqua of the Back, and Knight Leader. Moreover, they may have also been empowered by Curtana Original after Queen Elizard used Union Jack to distribute its power to all the citizens in the United Kingdom, and later aid against Carissa. They may have also witnessed Touma destroying the Curtana Original and defeating Carissa.

Kanzaki and the rest of the Amakusa Christians later treat the wounded after the end of the coup d'état. Saiji states that since Touma got the best part in ending the crisis, Kanzaki once again owes Touma again. Kanzaki tries to persuade them that she has no debts as everyone joined forces and the achievements should be divided equally. But the Amakusa Christians do not listen and instead, argue about which maid outfit Kanzaki should wear. They may also have gathered around Index after Fiamma of the Right took away the external controller for her John's Pen Mode, as well as Touma declaring to hunt down Fiamma of the Right.

World War III Arc
Along with their Priestess, the Amakusa Christians participate in the Battle of Dover Strait, anticipating the French crossing its waters. Agnese Sanctis notes on how the world has changed and later notes that it is 100% perfectly accurate to say that French forces are going to invade England through Dover Strait, which was confirmed immediately afterward, as 1,000 French magicians walk on the sea's surface by solidifying it. With the initial assumption that there would be a naval battle, their ships and their tactics are now rendered useless, Kanzaki and the Amakusa begin their battle against the French, and are later joined by Princess Carissa.

When Lessar tries to seduce Touma hundreds of miles away from the Battle of Dover Strait, Itsuwa feels a chill along her spine, to which Saiji asks what's going on, though she states to him to pay it no mind. They later witness the arrival of the Mobile Fortress Glastonbury and the ensuing clash between Carissa and the Maiden of Versailles.

The Amakusa Christians most likely later joined Kanzaki and the Agnese Forces to go to the Eurasian continent, towards the Russian battlefield where both Academy City and Russian soldiers have collapsed. They later witness another Golden Arm pop-up nearby, which is later cleanly cut down by Kanzaki Kaori, shocking the soldiers present.

Homecoming Arc
In St. George's Cathedral, as Itsuwa becomes frantic due to the information that Touma is still alive and in Academy City, Saiji offers her a bamboo sword to spar in order to clear her thoughts. Angelene, seeing this, calls out to Lucia regarding a "samurai battle" that is taking place, but is scolded by Lucia for cheering on a fight, unbefitting of a nun. Angelene becomes excited, however, and references, trying to imitate the blade catching technique.

Seeing Angelene's excited demeanor, however, makes Saiji nervous, as it would seem that not pulling it off would make Angelene disappointed. Saiji tells Itsuwa that they have no choice, and tosses his bamboo sword aside, in order to try out the sword catching technique, which surprises Itsuwa enough to raise her voice and gather more nuns towards them as well as the other members of the Amakusa. Itsuwa attacks Saiji, and he is unable to catch the sword, hitting him on the head. Because of this, however, Itsuwa sees the need to follow through, for the sake of Saiji as it would be embarrassing. She tells Saiji that it was just a practice run, as such, it doesn't count. They try again, and Saiji is hit in the head again, much to both their frustration. Kouyagi then comes up and offers them an imitation sword steel-forged sword, after Saiji tells her that the bamboo sword throws her off her timing. Saiji is expectedly horrified with it and is then hit in the head again by Itsuwa, but this time, with the iron-forged sword.

As Saiji writhes in pain, Itsuwa still complains that her timing is off and that a real sword is needed for Saiji to catch it. Just then, Tsushima offers a real sword, a Bateren-dedicated Kanemitsu Toushou. Saiji is utterly terrified, as Itsuwa takes the sword and her face is shadowed as she prepares to finish their demonstration with Saiji. Angelene's eyes sparkle at the prospect of finally seeing the sword catching technique, but Saiji wants to back off. However, Itsuwa doesn't want Saiji to gain more shame. Seeing that Itsuwa will not yield, Saiji steels himself and hopes he'd gain some hidden ability like on those protagonists.

Coronzon Arc
During Crowley's Hazard invasion of the United Kingdom, he and the Amakusas were stationed on the frontline against the invaders crossing the Strait of Dover. After the coastal defensive line fell, they withdrew to London and regrouped in order to begin a counterattack. At the time of the events which transpired in Westminster Abbey, the Amakusas noticed the sudden disappearance of the Crowley's Hazards in the city. Before they could go to investigate the cause, they were found and defeated by the reproduced William Wynn Westcott and Annie Horniman.

Kamijou Arc
{{Main|Kamijou Arc} Tatemiya was present at Windsor Castle during the party celebrating Coronzon's defeat and was subsequently involved in the conflict which arose due to the emergence of the other Touma.

Toaru Majutsu no Index SS: Necessarius Special Admission Test
Saiji appears as a supporting character for the side stories while Ituswa is the protagonist. As the leader, he gives advice to Itsuwa, and leads the Amakusa Christians to try to clear their name by apprehending the true culprit of the ones who messed up their test, pretended to be Amakusa Christians, and took away the Necessarius Free Passes that allowed people to gain access into Necessarius facilities.

Abilities
As being part of Amakusa, all of what Saiji wears is part of his magic and is deliberate. The Amakusa Christian’s specialty is secrecy since they’re Christians whose nature is to deceive others; they hide the teachings of Christianity inside Shintoism and Buddhism completely and use rituals and techniques as part of their greetings, diet, and behavior in their everyday lives. They cover all their tracks so that others won’t even notice their existence. These teachings have been passed down from generation to generation.

As once the Substitute Superior Pontiff, Saiji is of course an expert of this. Like all the Amakusa Christians, he carries a weapon. He wields a 180-centimeter long, a 17th-century two-handed sword that originated in France. The unique characteristic of the flamberge was its undulating blade akin to a flame. It was said that the current design was meant to increase its destructive power. He is able to wield it expertly, cutting down several Agnese Forces nuns on his own. He has knowledge of Anti-Impact and Anti-Flame spells, barrier spells, and most likely other Amakusa-related spells. However, he is most effective in team situations, unlike the human wave tactics that the vast Agnese Forces, the Amakusa Christians, with its at least 52 combat-ready members,, have been shown to be much more focused on teamwork and unity.

Suppresses Fire
A spell apparently unique to Saiji due to his flamberge. By removing the flame attribute from it and swinging the sword around like a river to "suppress," he can suppress flame spells and send the heat and flames back, such as Stiyl's Flame Sword, which would then allow him to counterattack.

Design Evolution
Saiji's design remains fairly static throughout the series. His design is based on the "clergy" version, as Haimura put it, of the style usually taken up by the Japanese fashion.

Quotes

 * (To Touma from Volume 7): "However, since it’s already settled, this day next year will be your death anniversary!"
 * (To Touma, ibid): "Do we need a reason?... There’s no reason from the beginning. This is how the Amakusa does things, especially for our generation. You’re asking why our Priestess is able to be our leader at such a young age? In order to fulfill a child’s wish, she dared to go against a dinosaur that can swallow a mountain. In order to fulfill the dying leader’s wish, she was willing to protect a small village against thousands of enemies. Along the way, we were walking in her shadow. Although the time in which she led us was short, to us, it’s eternal... Because of her, we’re able to walk onto the path of righteousness; we’re not being led astray, and we don’t abuse our power. While it’s easy to just say it, she taught this through action. She used her actions to show that humans can be strong and benevolent, that doing this isn’t difficult."
 * (To Touma, ibid): "I thought that you’d go home quietly the moment I said that. In order to settle everything before you do anything, I talked it out with the Anglican, and now everything’s wasted. Seems like you’re a bigger idiot than I thought. However, I don’t hate such an interesting idiot like you."
 * (To Itsuwa from Volume 16): "The saviour that you so cared about was treated like that right in front of you, his body all battered badly. Being like that in front of him…you aren’t planning to do anything? That guy really went all his way to risk his life for such a woman? If so, that guy’s sacrifice was in vain, really in vain. The outcome is obvious, didn’t that idiot do something idiotic to save another idiot? Isn’t that how it is?"
 * (To the Amakusa Christians, his last instructions as the Substitute Pope, ibid): "Let’s go. Go to where the Amakusa should go!"

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Saiji Tatemiya