Index

Index(インデックス Indekkusu) is the eponymous character of Toaru Majutsu no Index. Also known by her full name of Index Librorum Prohibitorum, she is the main female character of the series and is considered the main heroine of the magic side. She is a member of Necessarius and has Photographic Memory and holds within her 103,000 grimoires.

Background
Much of her background is currently unknown because of the periodic memory lost that was brought upon her. It is not known if Index is her true name or that it is a name given to her because she holds within her the 103,000 grimoires. It is confirmed that Index was specifically chosen as the vessel for the 103,000 grimoires as she had the ability to perfectly remember things and that she was somehow unaffected by the books' madness-inducing effects and that a symbol implanted within her as a fail-safe when someone tries to remove the spell that would destroy her if her memories were not erased. In the manga it is shown that the ritual to transfer was done in Vatican by Necessarius.

Later after becoming the vessel of the grimoires she was given partners, probably as means for protection, three years prior to the start of the series she was the partner of Aureolus Izzard, then a year later with Stiyl Magnus. Index's relationship with her partners is unknown because of her periodic memory loss, but it is implied that they both Aureolus and Stiyl care for her deeply. It is confirmed that Kanzaki Kaori were best friends with Index.

The church has lied to Kaori and Stiyl, the churchplanned to make the grimoires harder to access by telling its underlings to perform "maintenance" on her mind in exactly one-year intervals once her memory has come to its "limit"; that way, she will not remember her close friends and accidentally and/or purposely reveal the contents of the grimoires.

Index somehow came to Japan a year before the start of the series, though by this time she already has lost her memories prior the time she arrived. Index eventually ended up in Academy City as she was being chased by magicians (Stiyl and Kaori, as it was time once again to erase her memories), moving from rooftop-to-rooftop during Academy City's unforseen power outage however she slipped and fell upon the balcony of the unfortunate Kamijou Touma.

Appearance
She has a small stature and a petite build, and much to her chagrin having flat chest which indicates that she is very young. She has silvery-blue hair that reaches up to her thighs, and have green eyes. She is often seen wearing her "Walking Church", a white modified nun's habit with gold highlights, it offered Index with ultimate protection from most attacks however it was destroyed by Touma's right hand, she still wears it though and applies safety pins on it to keep the garment together.

Personality
To complement her childish look, she also displays a childish personality. She is often elated by a variety of things and is slightly ignorant and curious of modern technology. She is also easy to irritate especially on Touma which usually ends in Index biting him. She also has an extreme appetite to the point that she would eat something that had passed its expiration date.

Abilities
Her sorcery name is Dedicatus545, "The lamb is devoted to protecting the wisdom of the strongest". She is capable of memorizing anything, as is one of the reasons why she was chosen as the vessel for the 103,000 grimoires.

According to Index she is incapable of doing magic, however when under Johann's Pen Mode she is capable of accessing the grimoires in her memories, including performing a complex magical ritual that healed her of all her injuries. It is unknown whether or not she was capable of performing magic before losing her memories. Her self-protection system will use the Feather of Light to force a reset on Index's own memory should a manual reset fail to be performed.

When Touma destroyed the symbol that was would destroyed her mind, while under Johann's Pen Mode she was capable of using very powerful spells such as St. George's Sanctuary and Dragon's Breath. She can also use Spell Intercept and Hell Fear.

List of Books in Index
There are 103,00 grimoires which Index holds in her memory, however there are a few instances where the names of the books of were explicitly stated, this a list of the books that were named thus far:
 * The Book of Eibon
 * The Lesser Key of Solomon (Lemegeton)
 * The Book of the Dead
 * Necronomicon - In reality is a fictional grimoire created by horror writer H.P. Lovecraft for his stories, it is unknown if the same applies to the Toaru Majutsu no Index universe. Seeing as it is one of the books stated that are contained within Index, it is assumed that their version of the Necronomicon is genuine in their universe.
 * Momatarou - According to Index the story is actually of occult nature and was disguised as a simple fairy tale told to children.
 * The Tetrabiblos
 * Houbokushi

Toaru Kagaku no Railgun
Index only makes small appearance in Toaru Kagaku no Railgun. Apart from her brief appearance in the 2nd opening where she was seen chasing someone (probably Touma), she appears in episode 17 of the anime where during she met Tsuzuri Tessou during her patrol, here she introduces herself as a sister and not a student and is seen fighting against a cleaning robot who cleaned up her donut. She later appears in episode 19 where Touma is looking for her, her appearance is somewhat obscured though she is seen eating food prepared by the Tokiwadai Dormitory for their visitors, it is implied that she is the glutton that Tsuchimikado Maika referring to earlier in the episode.

Finally she is seen in the epilogue of last episode where she is drinking a soda with Touma.

Index and the Church of Necessary of Evil
Index meets Touma on his balcony demanding him of food. Index introduces herself as a nun of Necessarius known as Index and that she is being pursued by magicians as they after the grimoires that she has, Touma was skeptical of the existence of magic but was quickly proven of it as he destroyed Index's "Walking Church" using his right hand. Index decided to leave Touma as she didn't want her to get involved, forgetting her headdress while leaving, because of this she needed to return to Touma's apartment to retrieve it but was attacked by Kanzaki Kaori seriously injuring her.

During Touma's battle against Stiyl, Index under Johann's Pen Mode she aids Touma by telling him that Stiyl is using ruins that is helping Stiyl. After his defeat Touma takes Index to Tsukuyomi Komoe as she was not an esper and was capable of doing the ritual to heal Index. Index being under Johann's Pen Mode finished the healing ritual with Komoe by summoning a replica of an angel, while chanting, she then falls unconscious.

When Touma returns she tells him the existence of the Church of Necessary Evil, also known as Necessarius. Later she and Touma go to a bath together where she reveals that she has lost her memories of the previous year, however she assumes that Touma is angry about this and runs away. She later discovers that Touma has been beaten to unconsciousness and that he has been sleeping for awhile, she then discovers Stiyl and Kaori has come for her but believes that they are after Touma, she tries to defend him but they leave anyway.

While resting Touma discovers the hidden mark within her that could destroy her if her memories aren't periodically erased, because of this Johann's Pen Mode activates and attacks Touma, Kaori and Stiyl using Dragon's Breath. Kaori and Stiyl discover that they've been tricked by their church into believing that they needed to erase her memories. With the efforts of Kaori and Stiyl, Touma is able to defeat Index(and in the process destroy Tree Diagram accidentally) but with the price that Touma and his memories of her are destroyed.

Index visits Touma in the hospital, where the frog-faced doctor tells her that his memories have been erased. Even then Index pleads to Touma to remember her, asking him things that had happened between them recently and that she loves him. However Touma surprises her that his memories were not really destroyed and that his right hand had fixed the problem, however Index becomes upset at this and bites him and then leaves him. However it is revealed that Touma was lying about his memories in order for her to not see her cry, meanwhile Index is walking away truly happy that Touma remembers her.

Himegami Aisa: Deep Blood
Index and Touma go to a restaurant with Tsuchimikado Motaharu and Aogami Piasu where they meet Himegami Aisa, Index argues with Aisa after the latter claimed that she was a magician however their argument was cut short when Aisa's teachers came to pick her up. When walking with Touma home she discovers an abandoned cat and decides to take care of it much to Touma's disapproval, however the cat runs-off and she tries to give chase though suddenly she notices someone applying a magic spell and decides to investigate leaving Touma alone. When she returns to Touma's apartment she carried with her the cat and named it Sphinx, Touma disaproved at first but somehow allowed Index to keep Sphinx much to Index's delight.

After Touma left Index ate the pudding in Touma's refrigerator, when Touma calls her he scolds her for it but later disregards it. Later when Index is taking a bath she remarks on how Touma simply disregarded her eating the pudding and decided to go find him. Index later arrives to the Misawa Cram School where she meets Aureolus Izzard though he is familiar with her, she has no idea who he is as her memories of him were erased, Index is later struck unconscious and slept through the whole battle between Aureolus and Touma somehow dreaming blissfully of Touma and telling him that she is hungry.

Index with Aisa later visits Touma in the hospital bringing with her Sphinx, she tells him that the chruch is going to take care of Aisa from now on. She proceeds to eat the apples that Stiyl gave to Touma before Sphinx wreaks havoc on Touma's hospital room.

Misaka Mikoto, the SISTERS and Accelerator
Index with Aisa try to find ways of trying to get rid of the fleas that are infesting Sphinx until Touma comes home along with Misaka 10032 much to Aisa and Index's chagrin, Misaka 10032 helps get rid of the fleas on Sphinx using electrical abilities and proceeds to lecture Touma on how disinfect their room of the fleas before leaving. Index decided to go to Komoe's house for food seeing as Touma has yet to return home. During their time in Komoe's house Index helps herself to her food, here Komoe explains to Index and Aisa on how esper powers work using Personal Reality, Komoe uses a chocolate ball inside a box to demonstrate this to Index where the latter is frustrated that she can't figure out what the box holds.

They later go to a public bath drinking milk and enjoying a massage chair, Komoe continues to explain to Index and Aisa esper powers and the strange occurence of Level 0's in the city, she inadvertently revealed that many "naughty" things happened withTouma while blushing, which irritates Index and Aisa.

After Touma's battle with Accelerator, she once again visits him in his hospital room. She bites him and then hugged him stating that she was worried about him, she asks him what he fought for this time, which Touma says that he fought for himself.

Angel Fall
At Komoe's insistence, Touma and Index go to the beach for a vacation until the heat on them by "higher-ups" goes down. Index shows-off to Touma her new swimsuit and gives him a jellyfish to the face confusing it for a hat. Index later get disappointed when she discovers that Touma's parents arrival will be delayed but Touma comes her down.

During the part where their appearances are switch, Index switches appearances with Aogami Piasu much to Touma's horror. For the mos part of the arc, Index gets abused by Touma for looking like Aogami Piasu and coming on to him. When they return to normal, Index derides Touma for her abuse at his hands and punishes him by biting him.

The Fake Date and the Kamijou Faction
While Touma is in his fake date with Mikoto unbeknowngst to Index, she is watching Magical Girl Kanamin intensively until Touma calls her asking her if she is alright and that a magician is in the city, she aids Touma by telling him the nature of the weapon the magician is using that he is wearing a disguise, he is cut-off from her before she can berate Touma again.

Yamisaka Ouma (Toaru Majutsu no Index Manga and Light Novels only)
Index and Touma go to a diner while Touma is working on his homework, Index lectures Touma on the he is working on that it is a veiled occult book and it is one of the 103,000 grimoires within her before getting attacked Yamisaka Ouma. Despite Touma's efforts she is kidnapped by Ouma.

During her captivity it is revealed that Ouma is trying to pull a book from her that will cure any sort of ailment because of a woman he had fallen in love with, Index pleads with him to stop as it would be harmful to Ouma all the while Touma heres the events unfolding using the cellphone Touma gave to her.

Touma arrives just in time and stops the ceremony before any further damage could be done to him, here he proposes to remove the curse that the woman Ouma fell in love with using his right hand.

Accelerator and Last Order
Accelerator passes through Touma's dorm where Index and Touma are arguing before he blocks the sound out with his vector manipulating powers.

Kazakiri Hyouka and the Imaginary Number Sector
Index follows Touma to school because she is worried that she will not get lunch, she successfully finds Touma's classroom but is then swiftly told by Komoe to go home. Index meets a mysterious person named Kazakiri Hyouka who helps her use a vending machine, they become quick friends and Hyouka helps Index fit in by showing her and wearing the school gym uniform, their fun is however cut-off when Touma accidentally walks into them. Index introduces Touma to Hyouka and that they are friends, she also warns Hyouka of Touma's tendency to attract women before they are interrupted by Komoe and Hyouka suddenly disappears. Index is later seen depressed because he believes that Touma is angry with her and that she hates him, Hyouka however consoles her tells Index that Touma is angry for her sake because they are friends. Touma finishes his class and keeps his promise in going out with Index, he also invites Hyouka to come along.

Index is very enthustiastic when they visit the underground mall, Index and company eat and also play games, and once again Touma accidentally sees them wearing revealing clothes which Index promptly punishes him for. Their fun is cut short when they are forced to evacuate due to a disturbance by a terrorist, however they learn that it is a magician. Touma decides to protect everyone with his right hand but Index is against this because it is her job to go against magicians, when they hear footsteps approaching Index and Touma trip on each other. Index then meets for the first time Misaka Mikoto and they do not get along very well, both of them demands answers from Touma on why the other is hanging out with him. Touma asks Kuroko about the situation and says that there is a terrorist in the underground mall and that as a member of Judgment and being a teleporter it is her duty to evacuate civilians. Touma asks Kuroko a favor to teleport Index and Hyouka away but Index disagrees since Mikoto would have time with Touma, Touma then asks Kuroko to teleport Hyouka and Mikoto but disagrees since he would have time with the midget (Index). Because of this Kuroko is prompted to teleport both Index and Mikoto away.

Later outside Mikoto and Index complain about the hot weather, there Mikoto asks Index why she is wearing a habit under such weather and then asks why her garment is ruined which Index says to Mikoto that she doesn't want to remember why it got ruined. Suddenly Sphinx runs away and prompts Index to give chase leaving Mikoto behind. However Index comes face-to-face with a golem by Sherry Cromwell, whose target is now Index. Even if Index cannot perform magic, she is successful in holding back the golem by intercepting the commands given by Sherry to the golem using the safety pins that she uses. However the golem no longer receives commands from Sherry and has now began moving automatically, making Index's situation grim as she can no longer disrupt the golem's movements. Just then Index is saved by Hyouka who reveals to Index that she is not really a human and that monsters should be fighting monsters, even with Hyouka's vast amount of power she is unable to hold-off the golem, she is saved by Touma who finally destroys the golem.

Index later confronts Hyouka about this but she simply hugs her, confirming to Hyouka on Touma's statements that she is still human regardless of what she is. Index says her farewell to Hyouka as she is returning to the Imaginary Number Sector, she tells Index that she will still be on her side even when she's gone, Hyouka promises to meet Index again one day before fading away.

Toaru Majutsu no Index-tan
Toaru Majutsu no Index is subjected to J.C. Staff's parodying, like Shakugan no Shana, Index is turned to a miniature version of herself albeit with a strange marking on her left eye called Index-tan. In the first sketch Index-tan reenacts her meeting with Touma but is then taken away by a bird and is presumed to have been eaten. Index-tan is later seen eating on top of Touma's head a'la Shana-tan and then proceeded to imitate Shana-tan, Index-tan later urges people to buy the Shakugan no Shana DVDs. During the part where Touma insert his right hand inside Index-tan's mouth to disable the magic within her, Touma says "such misfortune" after being vomited upon by Index-tan. Finally Touma and Index-tan watch a commerical featured by Motoharu and Aogami Piasu, asking Index-tan to be quiet after her amazement.

In the second episode, Touma meets Index-tan again and instead of being taken by a bird she is taken by a cat. When Touma is waiting for Hyouka and Index-tan in a changing booth, he comments on how they are mumbling the song they are singing as to go around copyright laws. When Touma is the hospital he is visited by Index-tan and a badly disguised Kuroko, who mistakes the antics of Touma's voice actor for his.

Shakugan no Shana-tan Revenge
Index-tan makes a cameo near the end, inserting herself in one of the sketches Shana-tan performs. Here Index-tan remarks that she is hungry while Shana-tan demands Index-tan to go back to her own show, they argue on how Index-tan was only asked to appear on her show. It later pans out to one of the characters of Shakugan no Shana remarking on the appearance of Index-tan and that she is an amateur (refering to her voice actress).

Trivia

 * It is a recurring gag for Index to bite Touma whenever he has inadvertently annoyed or irritated her in some way, however she has somehow stopped doing this after volume 11 of the Light Novels
 * Index is still wearing her Walking Church even though it has lost it's powers.
 * Index is still the only girl to have confessed to Touma, however Touma paid no regard to this.
 * Index's bust size has increased a little bit as evidenced in one of the illustrations of Volume 16.