Three Stories Arc

The Three Stories Arc is a story arc that occurs in the Toaru Majutsu no Index storyline. The arc focus on three separate event that happen on August 31; two stories focuses on Touma dealing with magicians while the other focuses on Accelerator dealing with the aftermath of the Level 6 Shift, which would mark the first time Accelerator is featured as a protagonist to the science side.

Etzali and the Kamijou Faction

 * Main Article: Etzali

A month before the events of the arc, Etzali was tasked to infiltrate the Kamijou Faction, after being deemed by his magic cabal, the Return of the Winged One, as a threat to the balance of the magic and science side. As such, he enters Academy City and later abducts Unabara Mitsuki, the grandson of Tokiwadai Middle School, in order for him to steal his image and form and to get closer to Misaka Mikoto, and eventually take her form and then later take down Kamijou Touma, however, he unexpectedly falls in love with her.

Aftermath of Level 6 Shift

 * Main Article: Level 6 Shift

After the defeat of Accelerator by the hands of Touma, the level 6 shift experiments involving the 20,000 sisters had finally ended. As a result, Amai Ao - investor and director of the experiment - is heavily indebted after the failure of the project and installs a virus into the 20001st sister Last Order. As part of a self-defense program, Last Order breaks out of her incubation chamber in order to seek the help of Accelerator.

Yamisaka Ouma

 * Main Article: Yamisaka Ouma

At an undetermined time prior to the beginning of the arc, Yamisaka Ouma had met a girl in the hospital whom had cursed markings over her body. Mistaking him for a funeral worker, the girl had several conversations with Ouma who had begun to realize that this girl was cursed to die and that she had accepted her inevitable fate. Over a period of time, Ouma began to fall in love with the cursed girl and seeked to save her life through magical means. On August 31st, he enters Academy city in hopes of extracting a grimoire from Index that will presumably save the life of the woman he loves.

Prelude
August 31, 12:00 AM. Touma discovers in the middle of the night that due to his excursion during the summer with the magic and science, he has yet to do any of his summer homework, with roughly 24 hours left for him to do it all.

Meanwhile, at the same as this, Accelerator passes by the Kamijou Residence after defeating a dew delinquents trying to attack after discovering that Accelerator has been beaten by a level 0. Accelerator notes that there is something different about him after being defeated by Touma. He later discovers one of the [Radio Noise]] clones following her, Misaka 20001, also known as Last Order. She tells Accelerator that since he has connections with research, he might be able to contact them to help her as to get her to an incubator since her body is still incomplete, though Accelerator is apathetic about this, Last Order continues to follow him, eventually arriving at his apartment, where both she and Accelerator discover that it has been ruined by persons unknown. Regardless of this, Accelerator allows Last Order to stay in his apartment overnight; Accelerator later sleeps afterwards.

August 31st, Morning
August 31, 8:00 AM.

Misaka Mikoto makes an attempt to enjoy her final day of summer vacation by (somewhat involuntarily) going out to buy a manga for Tsuchimikado Maika. As she heads out, the grandson of the director of Tokiwadai Middle School - Unabara Mitsuki follows her; determined to accompany her wherever she plans on going. Conveniently, Touma, Motoharu and Pierce happen to walk by, and as a last ditch effort to rid herself of Mitsuki's company, Mikoto claims that she was waiting for Touma for a date.

After getting Touma to agree with her plan, Mikoto explains how she’s been continuously stalked by Mitsuki and decides to take the opportunity to convince him that she’s going out with Touma in order to get him to lose interest. In an effort to look more like a couple, Touma and Mikoto decide to have idol talk which eventually leads to Mikoto informing Touma that less than 10 sisters still reside in Academy City after the events of the Sisters Arc while the rest are out getting bodily repairs outside of the city. After easily helping Touma with his homework, Mikoto leaves Touma to go get drinks; while waiting for Mikoto, Touma spots Mitsuki and engages in conversation quickly learning that he genuinely likes Mikoto.