103,000 grimoires have been contained inside of Index, and as a result she can only use 15% of her brain. This is her power of recollection, however, because of this each one year cycles requires for her memories to be erased lest she dies. That fact has been beaten into Touma's head, the fact that she may never even know that she had contact with him in the first place. The time limit is 12 midnight, and once pass it, Index will die. As such, Touma is allowed to say goodbye to Index. However, as Index's nightmare begins and her body experiences great pain and severe fever, Touma tries to find some way for her to live without erasing her memories. All efforts are in vain however, as Kanzaki and Stiyl appear before him. Is there a sure fire way for Touma to save Index?
Komoe leaves Touma and Index alone for the entire evening. Index lies sleeping on the futon; Touma recalls earlier on how both Stiyl and Kanzaki willingly left them as they would return later, and expecting Touma to not flee with Index, and having Index collapsing immediately after. Touma later gets a call from Kanzaki, she tells him that the limit is at midnight and they are preparing their schedule to finish in time, she tells him that the reason why she is telling him this is that she wants Touma to say his farewells. Touma asks if magic can't really solve anything, Kanzaki tells him that the church fears Index's rebellion as the holder of the 103,000 grimoires as such the church may have done some precautions as so Index would be unable to learn a spell to cure her. Magic can't save Index. However, Touma asks Kanzaki if "they" are able to do something, the science side.
Touma says that their side may find the way to cure Index; however, Kanzaki says that the magic side do not trust his betting on the side, as he has no evidence to support that it might actually help Index. Touma then resolves that he will find a way for himself and that he will steal the heroic moments from them, intrigued by this, Kanzaki tells Touma to show them how he will struggle through it until the end.
Touma starts researching about memory loss, and later realizes that he can ask Komoe to introduce him to neurological or mental research institutes. He tries to contact Komoe, but she is busy enjoying her bath and cannot get to her phone. Touma then opts to call random places to help him, however most if not all of them have already closed down for the night, he finds one that is still operating, but is turned down because they believed Touma was fooling with them. Touma realizes that is already midnight and Index has begun breathing heavily.
Kanzaki and Stiyl arrives to erase Index of her memories, however, Touma is still adamant that Academy City but is chatised by Stiyl. He later shows Touma a magical cross that is necessary for memory erasure, and challenges Touma to dispel the magic within it, if he is capable of saving her without erasing her memories; Touma is however unable to do it, and Stiyl leaves to continue the ceremony in erasing her memories. Touma in despair asks them to allow him to say his goodbyes to her; though reluctant at first - and with a little prodding by Kanzaki – Stiyl allows Touma to have some time alone with Index.
They leave, and Touma is left alone with Index who awakens. Index notices the symbol drawn by Stiyl on the wall for the ceremony, making Index worry; however, Touma calms her down and apologizes to her, and says that he will become stronger and never lose again to those who have made her this way. He asks her to wait for him, and that he will save her all the way next time. Index smiles and says that she will wait for him, before falling asleep again. Touma continue to reprimand himself for failing to save her, after she falls asleep, however he becomes suspicious of the information regarding Index's brain.
Because of the suspicion behind the information regarding Index's brain, he calls Komoe again – who finished her bath – and asks her about perfect memorization and the information that he was told. Komoe tells Touma that the human brain will not deteriorate if it can perfectly memorize anything, and can in fact store 140 years worth of memory. She goes on to say that the brain does not store memories in a single place, but rather sorts them out depending on what type of information it is; she concludes that it is impossible in neurology for the brain to break down, no matter how much knowledge is in it. With her lecture finished, Touma ends the call and focus her attention on Index.
Now knowing that Index shouldn't even suffer with the knowledge inside her mind, he concludes that the church lied to Stiyl and Kanzaki, and tampered with Index's body as so she would deteriorate if her memories were not erased every year, as such Index who possesses the 103,000 grimoires would be incapable of betraying them. Determined to save Index, Touma removes the bandages from his hand and touches Index's forehead hoping to dispel something, though there was no reaction. However, he notices a strange symbol embedded inside Index's mouth; Touma inserts his middle finger into Index's mouth, touching the symbol and dispels it.
Almost immediately, Touma is knocked back by the force and acquire injuries on his finger. Index rises and charges towards him, causing an explosion which alerts Kanzaki and Stiyl. A machine-like Index's speaks before them in monotonic fashion; she constructs a weapon from one of the 103,000 grimoires she has in her possession, a weapon that is the most effective against Touma, St. George's Sanctuary.
- Touma destroys Necklace and accidentally activates Index's John's Pen Mode.
- Index is seen using magic for the first time.
By order of appearance
No new characters were introduced during this episode.
- Imagine Breaker (not named) - Kamijou Touma Level 0
- John's Pen Mode - Index
- Memory Erasure Magic (not applied)- Stiyl Magnus
- Necklace (not named) - Index
- St. George's Sanctuary - Index
- The public bathhouse Komoe frequents.
- The episode features Touma crying for the first time.
- You can see the name Index Librorum Prohibitorum engraved on the back of the cross that Stiyl showed to Touma.
- Stiyl and Kanzaki are apparently applying the same technique Index used to heal herself back in episode 3, making the room into a temple and allowing an angel to descend to erase her memories.
- Stiyl references the Zodiac twice during the episode. First referring to Cancer, under the name of moonchild, which is another name for it, and then later referencing Leo.
- The symbol that Stiyl drew on the wall is an Unicursal hexagram.
- The symbol inside Index's mouth is ♃, which is the astronomical symbol for Jupiter.
- St. George is referenced during this episode, as the spell that Index uses against Touma. According to tradition he(St. George) is a Roman soldier and priest in the Guard of Diocletian, who is venerated as a Christian martyr. He is most famous in the tale of Saint George and the Dragon, where he slays the dragon in the tale.
- During the scene where Stiyl is drawing the hexagram, you can see that his hand and arm seem to stay at a single position; he should be unable to draw a hexagram large enough when his movements are like that.
- Who exactly lied to them about Index?
- How was the symbol applied to Index without the two of them knowing?
- Index: "You'll be alright. If I negotiate with them, your daily life won't get altered any further. I won't let them step any further into your life..." - said to Touma before collapsing.
- Touma: "Now that you've told me, don't you think I'd resist until the very end?" -said to Kanzaki on the phone.
- Touma: "Fine. Then I'll crush you, arch-rival. I'll save her and steal all the heroic moments for myself!" -said to Kanzaki on the phone.
- Kanzaki: "Show us a sensational struggle to the end..." -said to Touma on the phone.
- Stiyl: "Look at her! Can you spit out the same words in front of her? A person who has fought against this all her life... A patient who can't even open her eyes because of all the pain... Can you tell her to wait a bit because you want to try some stuff out?" -said to Touma after he asks them to wait a little longer.
- Stiyl: "So can you still do it? In front of her? Can you still take this away in front of a girl in that much pain? If you trust your abilities that much, then do it! You blasted mutant that thinks of yourself as a hero!" -Stiyl's challenge to Touma to dispel the cross that would help erase Index's memory.
- Touma: "Why...Why don't I even have the ability to save one girl in pain?"
- Kanzaki: "The night when we swore to erase her memories for the first time, we wept next to her the entire night." -said to Stiyl.
- Touma: "Sorry. I'll become stronger. I won't ever lose again. Those people that treat you this way, I'll kick every one of their butts, that's how strong I'll become...Wait for me. This time... This time, I'll save you all the way." -said to Index.
- Touma: "I'm not pretending to be a hero. I will become one!"