The City Academy is a city dedicated to science experiments and educational background, where most citizens are students and a large percentage of buildings are schools of different levels.
Rare events occur, which lead to Touma to discover the existence of Neccesarius, a religious organization, which uses magic and it's an opposing force to that Espers are the "science side" of City Academy, in some magicians psychic conflicts, Touma meets people who give a great turning point in his life, as his inseparable companion Index, and must make decisions that will decide the victory of one side or another.