After school, Touma and Index go the Underground Shopping Center with their new friend Kazakiri Hyouka. Three people, enjoying cosplays, meals, and games, to which Index concludes must be the essence of "school life". Suddenly, they are stopped by a Judgment girl, who tells them that Academy City has been infiltrated by a terrorist and that they must leave the Underground Shopping Center before the dividing walls close. As the people evacuate the mall, the three of them find something strange—an eye of a golem stuck to a wall. A killing intent came from the eye, and it speaks that it has found its target. Touma tells Index and Hyouka to leave. However, before comes Misaka Mikoto and her underclassman Shirai Kuroko, to make sure the evacuation goes smoothly. There, however, Mikoto and Index seems getting ready to fight with Touma as the center!?
Back in the Underground Mall, Touma, Hyouka, and Index, comes out of restaurant satisfied. They pass by an arcade, and in Index's naïveté assumes it is a television. Suddenly, Touma receives a call, and then suggests Index and Hyouka to enjoy themselves while he takes the call. He answers the call, but only receives a terrible reception, understanding nothing before the line is cut. Touma assumes it is because they are underground, and pay no mind to it. Meanwhile, Index enjoys the arcade, viewing the toys in the crane game with much glee. Index then notices two girls in playboy bunny outfits, conversing about the various cute outfits they could aware. They then enter a photo booth and take their pictures together, which entices Index. Hyouka then points that they can rent clothes for photo printing as well, much to Index's excitement, and then takes the helpless Hyouka by the hand and drags her to try on a view of them. At this moment, Touma happens to pass by and is looking for Index. He then notices Index's voice, talking about Magical Powered Kanamin's dress. Beyond all judgment, Touma comes closer and calls out her name. To which, Index nervously replies. Hyouka tells him that they'd be troubled if he comes in now. As if to test the Fates, Touma confidently says that he won't make the same mistake he made back in the nurse's room. Like clockwork, there is some pushing from the inside, and the curtain falls, and Touma once again sees Hyouka and Index not yet decent. It is known what happens next, and Touma's screams fill the air of the arcade, which falls on apathetic ears.
Despite that, Hyouka and Index manage to take pictures together. Touma with them, still fills the effects of Index's punishment, while Index gives half of the pictures to Hyouka, which blushes afterwards. Index is having so much fun, she declares her excitement of "school life". However, Touma points out the other part of school life. However, their conversation is cut short as they discover that the entire mall is devoid of people, and a voice is apparently talking directly towards the girls, though Touma could not understand this, despite Index and Hyouka's description. Suddenly, a girl with a brown vest, comes running towards them, demanding their attention. She is of Judgment, and she apparently been calling attention all this time, and is angry on how Touma is ignoring her. Touma asks what she wants, and the girl is obviously frustrated, asking if she has heard voice through her telepathy. She tries to use her power on Touma but to no avail, as the Judgment girl just tires herself out. Having no choice, the Judgment girl tells them that a terrorist has come down into the Underground Mall. She informs them that the walls be lowered and the mall will be closed off, and that they should evacuate immediately, the girl then leaves. Being smart about this, Touma tells the girls that they should go as well. They move out with throngs of people to the exit, in a calm and orderly fashion.
Suddenly, an echoing laughter is heard, and they turn to look and see an eye protuding from the wall. Here, Index becomes serious and immediately recognizes what the eye is, which Touma realizes that the terrorist is a magician. The magician speaks again and makes a declaration, and the immediately expounds and contracts, disappearing. Then, there is an explosive noise, and the power is cut in the entire mall. The people around immediately run for the exits before the gates trap them in like rats, though some are of course left behind.
Seeing that it's time for him to do some work, Touma tells Index that she should go with Hyouka and hide somewhere, but Index insist that he and Hyouka instead go and hide, as the enemy is a magician and therefore, it is her duty to confront her. Touma asks rhetorically on how Index is able to fight with such thin arms. This angers Index, asking if Touma is beginning to think his lucky wins are actually because of his skill. Touma counters that he cannot possibly have any luck, inadvertently insulting himself, and notes, much to his dismay. Hyouka, being ignored all this time, asks if there anything she could help with, but is denied by the both of them immediately afterwards. Suddenly, they hear footsteps echoing in the abysms of the dark halls of the underground mall, and assumes it is the enemy. In an instant, both Touma and Index, tell each other to hide as the both of them try to confront the oncoming sound, of course, this has led to something unfortunate, as both of the trip each other, with Index on top, making Sphynx mew in turn.
On the other side, the footsteps are apparently from Kuroko and Mikoto, who hear the cries of that little kitten. They turn a corner, to which the both of them see in full view what has occurred—Index and Sphynx on top of Touma. It is known on how this turns out. Mikoto asks Touma what he is doing, a situation that Kuroko does not ignore, teasing Touma and Index. Index of course, does not take this lying down, asking Touma the identities of the classmen women in front of them, and asks if they are his acquaintances. Mikoto is irritated, and calls out Index calling someone she met for the first time "classless", and what her problem is. Index stands up, and quickly concludes that they are indeed Touma's acquaintances, and asks Mikoto's relationship with Touma. Mikoto cannot answer straight, and takes the question back to Index, asking what she is to Touma anyway, all the while, Kuroko looks blankly on the side. Index answers Mikoto, and tells her that Touma is her saviour, to which Mikoto asks if she is another of those persons who were helped by him even though they didn't ask for help, to which Index nods, and in sync, the both bellow out a sigh, before calling ot Touma, and demands an explanation from him. Touma stutters, at which point Kuroko snidely remarks on how, Mikoto has given herself up to "Kamijou-san", and starts laughing, though Mikoto tries to denies this with a red face. Mikoto finally asks Touma what kind of trouble he has gotten himself into, to which he nonchalantly answers that he does not know, and asks Kuroko, of Judgment, for some answers.
Kuroko briefs all of them. As you know, a terrorist has infiltrated the Underground Mall, however, she adds that a large-scale battle will most likely happen, and that it is her duty to evacuate the civilians that are still trapped, as she is a teleporter of course. Touma tells Kuroko that she should the girls out, as he would but them some time. However, both Index and Mikoto tell him that he should be the one running first. Touma is surprised, but does not yield. He restates that his right hand can neutralize any kind of power, as such he needs to stay here. Kuroko tells that she has a limit on her powers as well, as she is only able to teleport two people, excluding herself, at a time. With this, Touma decides that Index and Hyouka should be taken first. However, Index protests, and asks if he wants to be alone with the "short-hair". Hearing this, Touma then decides to take Mikoto and Hyouka, to which Mikoto contemptly comments on how it looks like Touma wants to stay with the "midget", letting out electricity as she does. With that, they have reached an impasse, much to Touma's dismay, and all the while, Mikoto and Index show their contempt for each other, despite the fact that they are currently all in danger inside an underground tunnel as there is a terrorist attack by a magician and all. However, Kuroko touches both of their shoulders, and wisely teleports them both instead, much to Mikoto's remonstrations and Index's confusion.
Touma sighs in relief after that insanity, and apologizes to Hyouka for having to stay in the underground as a terrorist attack is in place. Hyouka states that it's all right. Suddenly, there is another large explosive sound that rocks the ground on which they stand. Sounds of gunshot fire ring out in the distance, signaling the start of the battle. Touma apologizes to Hyouka, and asks for her to wait for Kuroko to come back. Hyouka asks what Touma is going to do, to which he states that he will go to stop the magician, and runs off before Hyouka could reply. Here, Hyouka could only watch as Touma's back becomes smaller and smaller, and more obscure, as the darkness swallows his form.
With their assault rifles firing, a line of Anti-Skill led by Yomikawa Aiho, attacks an inexplicable enemy, a moving rock humanoid—a golem. Meanwhile, Sherry is in tow, uncaring of any bullets that misses her golem, or the bullets that would ricochet from it. The helmetless Aiho points out the obvious, none of their attacks work, and that's terrible! His fellow Anti-Skill points out on how the evacuation of the students has not finished yet, and that they need to find a way until then. Meanwhile, another Anti-Skill member, beyond any reasonable judgment, tries to use a grenade in a closed environment, with predictable results. Sherry notices this, and commands his golem to attack, and the grenade explodes. Touma arrives, and sees that the battle has brought. He comes towards a bloody Aiho, and asks if she is okay. Aiho notices him and discovers that Touma is one of Komoe's students. The smoke from the explosion clears, and the golem roars. Touma valiantly answer its call, stepping forwards without fear, and without heed from anyone, especially Aiho.
Sherry notices his advance, and realizes that she is facing the Imagine Breaker himself, and not the key to the Imaginary Number District, though Sherry doesn't care as she says that the one she has to kill need not to be her. Sherry commands her golem to attack, and tries to punch Touma, though he neatly dodges it. Sherry says that her power is earth, and that one should be able to stand after confronting Ellis. Sherry introduces herself to Touma from the Anglican Church, though she doesn't care either way as he'd be dead. Touma is surprised on how someone from the same church as Index would come attacking, though Sherry then answers his question—she wants war. She declares that she wants a reason to a reason to start war, and that the more people that knows that she's from the Anglican Church, the better. She commands Ellis the golem again to attack, and once again, Touma dodges its attack. Although Touma knows that nothing will come out of it, as he needs to make contact with it for his power to work. Suddenly, Touma hears a voice, and its from Kazakiri Hyouka, who, for not apparent logical reason, has followed Touma. He calls her out for her dumb actions, though she fidgets with her answer, apparently oblivious to the Cyclopean rock monster in front of her. Touma tries to get her out of the way, and Ellis comes attacking them. With a punch on the ground and time seem to slow down significantly, Ellis sends forth several wicked missiles of stone towards them, and though Touma tries to protect her, a sickeningly dull sound hits Hyouka square in the head, dislodging her glasses. Touma goes towards her, but is shocked to see what he beholds. Shell-like, Hyouka's skull is hollow like Man's but that where the similarities end. Here, Touma sees a glowing prism revolving inside of her, and despite the damage done upon her, Hyouka still alive. She sits up without assistance, and tries to find her glasses. She touches the queer feeling on her face, and discovers the horrible truth. She is lost for words, and cannot understand what is happening, Touma tries to console her, but its too late. Hyouka breaks down and tries to run away, in the opposite direction, and is hit by Ellis Sherry's golem on her command for all her trouble. A sickening sound is heard as Hyouka's body contorts in terrible ways, but she lives. Some queer power forces her to stand up, and as she comes to, she screams, running away again. Sherry sees this, and commands her golem to collapse a ceiling, preventing Touma from pursuing her.
Meanwhile, Kuroko returns, looking for Touma and Hyouka. However, she notices a crowd still trapped inside the mall, and wisely chooses to evacuate them first instead of finding Touma and Hyouka.
Back with Touma, he tries to answer the queer questions that have popped up after the scene with Hyouka. Suddenly, his phone rings, and on the other line is Komoe. She is relieved to have finally connected with him, and that Aisa has tried several times to contact him, though all ending up in failure. Komoe says that she has something important to say, though Touma tries to end it as he has obviously other important matters to tend to, but Komoe says that it is about Hyouka. She says that Hyouka could not be seen on any of the school's cameras, and that they have no idea on how Hyouka was able to enter campus and sit next to him. Touma asks what it all means, and Komoe says that it has something to do with AIM dispersion fields which are related to Hyouka. Komoe gives a theory: bioelectricity, magnetic field, the act of breathing, and others, are human-like things that when gathered together should create a human. Komoe states that Academy City is filled with espers, and all of them unconsciously release AIM, and that something meaningful should be created if they are combined, and that something should be Kazakiri Hyouka. Touma is incredulous regarding this to which Komoe says that sightings of Kazakiri Hyouka have been occurring for a long time now, and that, back them, she was a vague and ghost-like existence. Touma tells Komoe that Hyouka does not seem to realize this fact herself. Komoe says that there shouldn't be any doubt in her mind if she assumed that she has always been a human. However, Komoe says that Kazakiri Hyouka is not a human, and that she is a physical phenomenon that the AIM Dispersion Fields of espers have given birth to. Touma thinks it's cruel, but Komoe states that even if we combine all the elements that constitute a human, Hyouka is still not a human, though, she asks what's the reason she cannot be considered human, and asks what Touma thinks of her himself. She asks if Hyouka was just an illusion that just stood, lifeless, heartless, and was doing nothing, and that was she an existence that was so light that she could abandon. Touma declares his stance, and states that even if Hyouka was an existence like that, she shouldn't just disappear like that. Komoe is relieved and laughs, proud on how Touma has gotten the right answer. She tells Touma not to make his precious friend cry, and Touma promises her. The call ends, and now, Touma is now more determined than ever.
Meanwhile, Hyouka sits alone in an abandoned hall, still reeling from the pain. Suddenly, the side of her face glows, and threads seem to be sewn to form again that which was once lost. Her face is whole again, and in her hand, a pair of glasses, clear and unbroken, are formed. She breathes in, and finally calms down, and wears her glasses again. Suddenly, another booming sound is heard, to which, much to her horror, Sherry Cromwell has found her at last. Sherry is with golem, and asks what she is, and tells that she is supposed to be the Key to the Imaginary Number District, though is incredulous of her form. Hyouka asks why she is doing such a cruel thing, and Sherry asks if Hyouka is one of those types that say "I'm scared of dying," and tells her to realize already that she is not a normal human. Hyouka is obviously shocked, though Sherry just taunts her reaction. Sherry commands her golem to smash its fist, and uses it's reforming abilities as a comparison to Hyouka's inhumanity―both monsters. Hyouka closes her eyes and recalls the moments she had fun with Index and Touma, her friends, where she was called a friend. Tears well up from her eyes, and Sherry just taunts her again, disgusted that such a being as her is crying. She commands Ellis to attack her, and Hyouka flinches. Then, a sound is heard that is not to be expected. When Hyouka opens her eyes, she sees before her, a certain boy, holding the entire force of a punch of a rock monster with a special right hand―Kamijou Touma, her friend.
- Sherry Cromwell, who is deemed as a terrorist, and attacks the Underground Mall.
- Misaka Mikoto and Shirai Kuroko meet Index and Kazakiri Hyouka for the first time.
- Kazakiri Hyouka discovers that she is not human.
- Kazakiri Hyouka
- Kamijou Touma
- Sherry Cromwell
- Shirai Kuroko
- Misaka Mikoto
- Yomikawa Aiho
- Tsukuyomi Komoe
- No new characters were introduced in this episode.
- Imagine Breaker - Level 0, Kamijou Touma.
- Index Librorum Prohibitorum - Index.
- Electromaster - Level 5, Misaka Mikoto.
- Teleport - Level 4, Shirai Kuroko.
- Ellis Golem - Pratical Kabbalah, Sherry Cromwell
- Regeneration - Kazakiri Hyouka
No notable locations were introduced in this episode.
- It took 22 episodes for the two titular heroines of the series, Index of Toaru Majutsu no Index, and Misaka Mikoto of Toaru Kagaku no Railgun, to meet.
- The episode confirms that Telepathy has no effect on Touma.
- Touma references the incident last episode where he sees both Hyouka and Index changing clothes in the nurse's room of his school.
- Index mentions Touma saving her life back in episode 6, though Touma has no memory of this. Mikoto also references Touma helping her from episode 10 to 14.
- The firearms used by Anti-Skill in the episode is a SIG SG552.
- The Anti-Skill uses a M67 grenade inside a tunnel. Despite having an injury radius of 15 meters, the Anti-Skill, specifically Aiho, Touma, and even Sherry, gets out relatively fine after the explosion.
- The videogames that appear in the arcade, also appear in episode 15.
- Mikoto has always been depicted as visibly taller than Kuroko, however, during the part where Kuroko decides to teleport both Index and Mikoto, she is shown to be just as tall as her.
- Why would Sherry start a war?
- Who exactly is Sherry's target?
- If Hyouka is an amalgam of all the AIM dispersion fields of espers in Academy City, then why is she specifically in the form of a high school girl?
- What is the use of that glowing prism inside Hyouka's head?
- How does Hyouka reform herself?
- Why did Hyouka appear to Index of all people?
- Touma: "This Kamijou Touma won't repeat the same mistake he made back in the nurse's room."
- Sherry: "Scream as much as you can in this mud-stinking tomb covered in clay!"―To Touma and company.
- Touma: "Hah! I thought you could come up with something better. This Kamijou-san, the manifestation of misfortune, cannot possibly have any luck... I hate myself for saying that..."―Touma accidentally insulting himself as he replies to Index.
- Kuroko: "My, my, getting so steamy so quickly?"―Regarding the situation Touma and Index are in.
- Kuroko: "I see... I thought it was fishy, but Oneesama has already opened her heart and body to Kamijou Touma, eh?"―Regarding the situation with Touma, Index, and Mikoto.
- Index and Mikoto: "You're the one that should be running away first!"
- Sherry: "Let's go, Ellis. Let us go hunt down the sorry and ugly little fox."
- Komoe: "Was she so light of an existence that we can abandon her?"―To Touma regarding his feelings on the existence of Kazakiri Hyouka.
- Touma: "No! Of course not! Even if she was just an illusion that would vanish when touched, that doesn't mean she could just disappear like that."
- Komoe: "There you go! Sensei loves little sheep that are brought up the right way!"―To Touma regaining his answer.