Itsuwa

Itsuwa (五和) is introduced in Volume 11 of the light novels, and is a 16-year old girl belonging to the Amakusa Catholic Church.

Appearance
Itsuwa is a young Amakusa girl with purple hair that extends just below her shoulders. She wears her hair in a bobcut with short fringes.

Itsuwa is rather well-endowed and her outfits consists of clothing worn in such a manner that much of her skin is exposed, though often not intentionally. In volume 14 she is forced to wear skimpy clothing because she has nothing else to put on after jumping into the river to save Touma.

Personality
Itsuwa is generally very friendly and warm. Like many other females in the series, she seems to have developed romantic feelings towards Touma bordering on actual love, but due to her shyness she has not been able to act on them or convey them to him. She states that even if her 'Supreme Pontiff' (Kaori- who is basically her superior officer) has feelings for Touma, she will never give him up to her.

Orsola Aquinas Rescue Arc

 * Main article:Orsola Aquinas Rescue Arc

She appears for first time in the anime giving the advice to the substitute Supreme Pontiff of the Amakusa Catholics, Saiji Tatemiya, about the preparations for the miniaturized pilgrimage before starting a fight with Anieze Forces.

Afterwards she joins the fight against the Agnese Forces and creates a diversion for Touma and Orsola.

La Regina del Mare Adriatico Arc

 * Main article:La Regina del Mare Adriatico Arc

When first introduced into the series, she appears alongside other members of the Amakusa Catholic Church, researching information on the remodeling of one of the Roman Catholic Church's artifacts. This is when she meets Touma in person for the very first time, after hearing from the other members of the church of Touma's prowess, facing 250 battle nuns on his own before back-up arrived from the Amakusa Church, Stiyl and Index. All of the Amakusa Catholics seem to show respect to Touma after hearing that he has also fought Kaori Kanzaki, seen her totally naked, received her Nanasen and has somehow managed to walk away from said incidents alive.

Terra of the Left and the Document of Constantine Arc
After Touma's involvement with the Amakusa Catholics and later, their agreement to aid Touma in Italy, Touma almost faints after being strangled by parachute strings after parachuting from a plane with Tsuchimikado. Itsuwa rescues him before he drowns. It is discovered that Amakusa catholics are gathering info in France on what is causing the disturbance, and Itsuwa finds Touma by pure coincidence as shown by her not knowing about why Tsuchimikado and Touma are there. They regroup with Tsuchimikado, then go to a nearby cafe to plan before making a move. Itsuwa explains how popes used to visit Avignon a couple of centuries ago, when France and the Vatican had a dispute and France emerged the victor.

The three are spotted by an angry mob before they can actually plan anything out. It seems that their animosity towards Touma comes after seeing him drop out of the plane. Tsuchimikado breaks off from the other two and Touma and Itsuwa start moving toward Palais des papes. While dodging the mob to get there, Tsuchimikado contacts them. It is revealed that he too is on his way to Palais des papes, but a wall of angry mobsters block his path. Touma and Itsuwa decide to cut the magical pipeline connecting Vatican and Avignon which allows the document to activate instead. This pipeline is basically a flow of energy that runs throughout the globe, and either Itsuwa or Tsuchimikado is needed to alter its path away from Avignon. The two end up at one of the many museums. Touma thinks about breaking the link using his Imagine Breaker but is told by Tsuchimikado that it might not work on the natural mana flow of the land, as there are exceptions to what the Imagine Breaker can negate. Just as Itsuwa is about to shut the pipeline using a magic circle made from common items such as a water bottle, a tour guide book, slippers and her own panties, Terra of the Left attacks them with a giant white guillotine blade, which Touma manages to block. The two then face off against Terra. Itsuwa uses 'Nanasen', and although the wires manage to wrap around Terra, they cause no damage to him. Terra comes through a wall behind Touma and attacks. Touma and Itsuwa find they can do nothing but try to defend themselves.

While this is happening, Itsuwa figures out that Terra's blade is made of flour, symbolising how bread is also the 'flesh of God' and the 'Fruits of the Earth'. Afterwards, Terra explains with a smile that he can alter the hierarchy of things. He reveals he put himself above the metal wires of 'Nanasen' so it didn't deal any damage to him. Tsuchimikado joins in the battle and attacks Terra with his magical origami and a handgun while telling Itsuwa and Touma to get away before the two collide. Before they can however, there's a huge explosion outside, which crumbles the museum wall. Academy City has sent their peacekeeping forces to attack Avignon.

Terra withdraws from the fight in order to secure the Document of Constantine and escapes. It turns out that's what Academy City is here for. Touma and Itsuwa pursue Terra while Tsuchimikado stays behind to try and stall the Academy City forces.

When Touma and Itsuwa reach Palais des papes, Terra appears again and attacks. Terra explodes his blade and shoots out pieces of it at them like bullets, Touma is unable to react but Itsuwa pulls him out of the way just in time and is struck in his place. Itsuwa is injured instead and Terra scoffs at her for being a dead weight, however, she tells him that she has found his weakness. Before she can speak again Terra attacks and knocks her unconscious.

Later, after Touma has already defeated Terra and is interrogating him about what exactly Imagine Breaker is, an attack from an HsB-02 blows the two of them away. Itsuwa regains consciousness and finds Touma again knocked out and injured by the HsB-02. Parts of the room are seen to have actually melted due to the sheer amount of heat and are covered in steam. Itsuwa overhears Accelerator speaking just as she is about to start tending to Touma. Accelerator is speaking with one of the higher ups of Academy City over the phone, telling them to send troops to come search for Terra's corpse and run DNA tests to see if he's really dead. She stays hidden, not knowing if Accelerator is friend or foe, steam giving her enough cover so as to not be seen. Accelerator leaves soon after to a deeper part of the palace. She states that she finds Accelerator, who can stand in flames like that, even more terrifying than Terra.

Itsuwa and Acqua of the Back's Attack Arc
In later events, she is assigned as Touma's bodyguard after Acqua declares he will come and take his life. When Acqua first attacks, she fails to protect Touma, trying unsuccessfully to heal him with magic several times. After Touma is sent to the hospital she is seen despairing because of her failure. She is rebuked by Tatemiya Saiji, who tells her to stop feeling sad and look to the future, when Acqua will come and attack again, and that she should focus on proving to Touma that it was worth his time protecting her from Acqua. During the Amakusa Catholics' rematch against Acqua, after Touma is very nearly killed, she displays a sudden change of personality, becoming full of tranquil fury to the point that even the way she speaks changes. Various male members of the Amakusa Church rebuke Tatemiya for going too far with his words, talking without thinking just to try and snap Itsuwa out of her despair. They complain about how they will all be traumatised because of seeing Itsuwa behave in such a way and that they will forever fear any woman that's in love.

War in Britain Arc
Itsuwa is browsing magazines in the Japanese District of London, trying to find ways to make Touma fall for her after hearing about how Kaori has made her move with the 'Ero-Fallen-Angel' cosplay. She despairs that because of how salient Kaori's move is, it's likely Touma has completely fallen for Kaori to the point that he might have even forgotten that Acqua has attacked him. She sees the 'Greater Spirit/Fairy' cosplay, and thinks about getting it in order to combat Kaori's attempt. She eventually decides not to go through with it while rumpling up her hair in embarassment at the thought. Itsuwa believes it would be too embarassing - and thinks this might be the difference between a normal person and a saint- a saint strikes decisively rather than having to think about it. In her deep thought she fails to hear the rest of the Amakusa's hiding in the attic and spying on her from a corner of the ceiling, talking about buying the cosplay first and giving it to Itsuwa - Tatemiya has somehow already got Itsuwa's three sizes and they plan to order the cosplay after all. This is all done so that they can witness a 'battle' between Kaori in 'Ero-Fallen-Angel' cosplay and Itsuwa in the 'Greater Spirit' cosplay.

Later, Itsuwa goes to pick up Touma and Index from the airport, only to find that Sphinx is the only one that has made the journey on the supersonic plane. She ends up drowning her sorrows at not being able to meet Touma at one of the houses in the Japanese District. Later still, other women from Amakusa tell itsuwa that the "youth with black spiky hair" has arrived, much to Itsuwa's horror as she is still half drunk and has bad breath. The youth in question walks in just as Itsuwa is preparing, but it turns out to be a practical joke played by Tatemiya, and Itsuwa in her fury throws a small table at him - knocking him off his feet.

When 'A New Light' infiltrated into London, Itsuwa went with the rest of the Amakusa Church to capture one of its members. Bayloupe escaped into the subways, and Itsuwa followed her. After a fight, Bayloupe managed to escape, but Itsuwa activated a machinism in the subways that directed Bayloupe into a Necessarius training area, which was a maze that tests a fighter's abilities and was unused due to people dying in there when the diffculty is set too hard. Itsuwa retrived the briefcase Bayloupe had and took it to Sherry Cromwell for her to investigate.

Fiamma of the Right and World War III Arc
When Lessar is later seen flirting with Touma in Russia, on the battlefield at Dover Strait where the British are fighting the French, Itsuwa feels a chill down her spine in a comical fashion. Tatemiya Saiji asks her what’s wrong but she replies that it's "nothing".

Abilities
Itsuwa is a user of the Amakusa style, whose magic can be activated using everyday items such as clothing, and has a wide range of effects. Due to the oppression of Christianity in Japan at the time of its founding, its magic has evolved in such a way as to make sure it's hard to detect, incorporating magic with everyday life actions, and most users of the Amakusa style are more proficient than other mages at distinguishing minute magical traits in a spell. Her weapon of choice is a Friulian Spear that can be disassembled and reassembled for the purpose of concealment.

More specifically, the abilities Itsuwa has displayed in the novels have been listed below:
 * Amakusa style combat: Itsuwa performs using her Friulian spear for single and melee combat, and can perform battle formations to boost her speed and agility to the point of equating Acqua of the Back.
 * 1) Nanasen: Similar to how Kaori Kanzaki can use the technique, however, Itsuwa uses her spear instead of a sword.
 * 2) Healing Magic: Itsuwa attempted to use this on Touma in volume 16, but it was negated by his 'Imagine Breaker'.
 * 3) Defensive magic: Which transfers part the damage she takes, into her clothes. She also has a spell that uses her clothing as a scapegoat.
 * 4) Forge Magic: The spell "Scattered Grass" improved her spear's durability by adding layers of reinforcement through resin. It turns her spear into a symbol of the 'Thousand-years tree', which symbolizes the growth of plants and makes certain spells more potent over time.
 * 5) Anti-Divine Magic: Developed by the Amakusa Church by merging Shintoism and Buddhism, Itsuwa with help from the rest of the Amakusa, can use the saints own energy to perform the 'Saint Destroyer' (Seijin Kuzushi) spell. This spell is stated to only work against divine beings like 'Saints' and does nothing to 'normal' magicians. Described in volume 16 as forcing the large magical energy that the Saints keep in check to go berserk and self-destruct. In the same volume, the first time it's used on Acqua it fails, due to Acqua's traits as part of the God's Right Seat in addition to being a Saint.
 * 6) Offensive Magic:  During the fight with Acqua, she used an explosive offensive spell called "Icy Night Wind" that tore apart the asphalt around them. 
 * 7) Curses of the Fallen: A punishment spell triggered by thin wires that can bypass any defense and create a chain of red mist explosions.

Trivia

 * Fans have speculated that Uragami, the Amakusa Catholic girl that Touma fought and saved from a fall in volume 7, may actually be Itsuwa. It is later revealed in the second season of the Toaru Majutsu no Index adaptation that Itsuwa and Uragami are two different persons.
 * Tsuchimikado once say that Itsuwa will dare to wear the erotic fallen angel costume without a second thoughts for Touma at Volume 16 epilogue.(This is Tsuchimikido prank to make Kanzaki to wear the erotic angle fallen costume)
 * Itsuwa use wet handkerchief plan to attract Touma so she can win his heart since at Volume 11