On the early morning of December 11, after dealing with the Kamisato Faction, Kamijou Touma returns to his apartment unit, only to find that most of the edible food ended up in the hands of the intruding Tsuchimikado Motoharu and Karasuma Fran, and the rest of the food have gone rancid in his absence. Motoharu later explains that he and Fran are currently fugitives after they shot Academy City's General Superintendent in the head, and Motoharu is trying to look for his younger sister Maika after directly attacking his former superior. Moreover, Motoharu is preparing to flee with Maika and Fran out of Academy City and into a location that is outside of either Japan or England. Touma is shocked not only because of the abrupt parting of ways, but also the fact that Maika still does not know anything about Motoharu's plans to leave the city. Regardless, Touma agrees to help Motoharu pick up Maika near District 7 Station, in spite of the increase of security caused by the 48 Hours to Restore Order and the attack on General Superintendent Aleister.
After making their way through Academy City that is undergoing reconstruction work, Motoharu and the others meet Maika, who is busy handing over warm meals for pedestrians, and Touma urges him to begin explaining his plans of leaving Academy City to Maika. To Touma's surprise, the conversation between siblings ended without a hitch, and Maika has even shown preparedness to deal with Motoharu turning into a fugitive.
Elsewhere, Misaka Mikoto had just been discharged from a District 7 hospital after her contact with the Anti-Art Attachment in District 11, being attacked by a "curse" and recovering with the help of a pirate-like girl. Despite the quick recovery, Mikoto remains uncertain of her condition. Eventually, she heads to Tokiwadai Middle School, which is quickly being rebuilt after the Element attack in several areas in Academy City, and meets Shokuhou Misaki.
Touma, Index, Othinus, Motoharu, Maika and Fran head to School District 11 by bus, and the serenity unsettles Touma, who had been used to being exposed to commotions recently. Moreover, Touma is frightened at the prospect of being held back a year because of his "adventures". After Othinus snaps him out of his fears, Motoharu and Fran begin discussing the dangers in crossing the wall that separates them from the Anglican Church team that was assigned to retrieve them outside. Afterwards, Motoharu prepares a drill and aqua regia that would dissolve electronics enough to weaken the security systems in the wall surrounding Academy City. Then, Motoharu assign Maika, then Fran, and lastly him (who can scale walls with ease) to scale the wall during the downtime caused by the corrosive aqua regia.
Maika successfully reaches the top of the wall when something attacks her. Othinus manages to prevent Touma from taking action using Imagine Breaker, and Index confirms that Maika was attacked by a curse that would destroy Maika's body from within if broken. With neither the girl with 103,000 grimoires in her head nor the Magic God knowing how to deal with the curse, Motoharu chooses to go against his initial plan and attack the Windowless Building together with Touma to confront the originator of the curse.
By order of appearance:
- Kamijou Touma
- Tsuchimikado Motoharu
- Karasuma Fran
- Hamazura Shiage
- Tsuchimikado Maika
- Misaka Mikoto
- Shokuhou Misaki
- Index Librorum Prohibitorum
- The narrative made references to the recent trend of light novel titling, where a concept is used as a story's title itself.
- Aqua regia is a corrosive mixture of nitric acid and hydrochloric acid, knowing for dissolving gold and silver, noble metals also known for their use in electronics.