As the Ichinaharan Festival is in full swing, powerful figures from the worlds of both magic and science rush to secure Frulein Kreutune after her escape from the Windowless Building. Gremlin dispatches Marianne and Thor. The magic side sends saints Brunhild and Sylvia. And Accelerator, Shizuri Mugino, and Mikoto Misaka set out from Academy City. Soon, battles between these monsters break out across town. But amid all the tumult, an injured Touma Kamijou attempts to find and save Frulein Kreutune before anyone else can get their hands on her!