Yamisaka Ouma

Yamisaka Ouma (闇咲 逢魔) is a Japanese magician introduced in Volume 5 who is adept in the use of a magical azusayumi crossbow which amplifies the power of his magic. He appears to capture Index in order to access a grimoire inside her that would allow him to save a woman who has been cursed to die.

Background
Not much is known about him, though what is known is that he visited a hospital where he saw a girl with cursed markings on her body. Noticing him, the girl had a conversation with him, with her mistaking him for a funeral worker due to him wearing a black suit all the time. Ouma realized that the girl had accepted her fate, and remained resolute through her suffering.

Ouma then fell in love with the cursed girl, and tries to find a way to save her. However, he feels that he has to commit several sins in order to achieve that goal and that she would be the reason behind those actions; thus, he denies to himself that he is trying to save her.

Appearance
He is a tall man who is often seen wearing a black suit and tie. His eyes are always closed except when he is in pain or experiencing some other strong emotion.

Personality
He aims to use methods that would mitigate casualties and destruction. He fell in love with a girl who was cursed to die yet refused to cry out for help. He originally claims to act for his own ends, but that is only because he doesn't want to blame his actions on and shift his sins to her.

Three Stories Arc
On August 31, Ouma appears during the afternoon searching for Index. Using his magical crossbow, he successfully manages to locate, and kidnap her while eluding Touma. He takes her to the roof of a building, and begins the ceremony of extracting Baopuzi, a Chinese grimoire that supposedly has a way to make someone immortal as well as a way to create a miracle drug that can cure any illness, the latter of which is his true goal in kidnapping Index.

Predictably, the knowledge of the grimoire he is extracting from Index painfully deteriorates his body. Index pleads him to stop, though he disregards her warnings and continues on. In one instance, Ouma's memory regarding the cursed girl flows into Index, and Index tells him that his rationalizations for denying the reason behind extracting the grimoire are wrong, as he truly wanted to save the girl because he has fallen in love with her. Though because of the sins he committed, he doesn't want her to be the reason for committing the sins. Index once more pleads Ouma who is now squirming in pain to stop, as his death may cause even more suffering for that girl.

Touma (who overheard the conversation between Index and Ouma through his cellphone) arrives just in time to destroy the ceremony, and chastises Ouma for trying to sacrifice his life just so he can save the cursed girl's, as well as making it seem like he was the victim. Touma then offers Ouma a deal: he would dispel the curse on the girl’s body using his Imagine Breaker, which he explains to Ouma can negate any supernatural phenomenon. The three of them later leave Academy City together, with Touma apparently successful in dispelling the curse.

Abilities
His speciality seems to be demon exorcism as he mentions he was able to bind a lower-class demon. All his spells use wind, and most of them have "Demon" in their names. He uses an Azusayumi (梓弓) normally used in ceremonial dances by priests and has the ability to fix damaged or distorted minds.

Spells:

 * Wind Demon's Bow String (風魔の弦): Uses the bow to create a ball of wind, which is then used to fly.
 * Piercing Bullet's Bow String (衝打の弦): Uses the bow to create a ball of wind, which is then used to blast through objects.
 * Seeking Demon's Bow String (捜魔の弦): Emits a radar to track down a target.
 * Severing Demon's Bow String (断魔の弦): Uses the bow to fire a high-pressure blast of wind.
 * Invisible Demon's Bow String (透魔の弦): Turns the user and those he wishes invisible.
 * Confusing Demon's Bow String (惑魔の弦): Interferes with the perception and memories of the target, and can allow the user to impersonate someone. This is what Ouma used to enter and leave Academy City.
 * Lantern Festival: By setting up a barrier that's mixed with Shinto and Buddhism, he can amplify his bow's power to draw out Grimores and read minds. However, this works both ways, so his target can read his mind as well.

Trivia

 * Though much of the Three Stories Arc is featured in Season 1 of the Toaru Majutsu no Index anime adaptation, Ouma's involvement in the story is omitted. However, both he and his story appear in the manga adaptation, as well as Season 2 of the anime adaptation.

Quotes

 * To Index: "There's nothing a magician can't do. I became a magician so that I'd never have to experience failure and frustration again!!"
 * In his memories: "Death is right in front of her, and yet she refuses to scream for help!!"
 * To himself: "But no matter how hopeless it seemed... I just couldn't give up on her."