A Certain Magical Index, Vol. 2 (light novel‪)‬

A certain unlikely hero...
In Academy City, where superhuman abilities are scientific reality, Touma Kamijou is trying to reconstruct a life for himself, but that's easier said than done with a girl by his side with the arcane knowledge of 103,000 grimoires rattling around in her brain...
Now seemingly inextricably caught up in a world where magic is a reality, Kamijou learns that a certain shrine maiden is being held captive in one of Academy City's cram schools. Can Touma ally himself with a sorcerer who has on more than one occasion tried to do him in? The only thing he knows for sure is that he really does have rotten luck...