A drunk lady encounters Accelerator and Kamijou Touma in two separate events; that lady, named Misaka Misuzu, is trying to head to Dangai University, where she is enrolled as a student. While Accelerator ignores her request, Touma decides to exchange numbers with the familiar lady who is Misaka Mikoto's mother.
To sate his curiousity about Misaka Misuzu, Accelerator contacts Tsuchimikado. However, the line is hijacked by GROUP's informant, who tells him of a mission to eliminate Misaka Misuzu. It turns out that Misuzu is trying to retrieve her daughter after the spread of news of war coming to Academy City, and the only way for it to be stopped is through killing her. Accelerator rejected the mission, but soon finds himself forced to accept it after discovering GROUP hijacking his choker.
Touma soon receives a call from Misuzu herself, who is now stuck as a hostage by Skill-Out inside one of Dangai University's lecture rooms. In spite of the trouble soon to come to him, he pushes on. Meanwhile, Hamazura Shiage, the substitude leader of the Skill-Out gang formerly led by Komaba Ritoku is now cornered after their plans fail without the presence of the old leader. They are now forced to take care of Misuzu themselves, and with the presence of Accelerator nearby, they are much more in danger than ever.
After a long run to Dangai University, Touma reaches the interior of the university and creeps past the bodies of knocked out Skill-Out, before reaching Misuzu. Touma soon dives into the heart of the battle and luckily survives due to Accelerator's unlikely intervention. He and Misuzu soon manage to escape the school compound. However, Hamazura Shiage emerges to pursue them.
Shiage becomes desperate to complete the mission, but Touma's strength was enough to stall him from taking away Misuzu. After a fistfight between the two Level 0s, Touma stands victorious. Soon, Touma is taken to the hospital for a terrible head injury, and there, Misuzu reveals that she was there to take Mikoto home; however, she reconsiders her decision after seeing how people close to Mikoto are willing to keep her safe.