Kamijo is a student at Academy City's school, which is a place where people employ science to improve their supernatural talents. Fortunately for a young nun who goes by the moniker Index, the guy has a lot of heart. She needs to get away from a society of sorcerers because they are after the incredible 103,000 volumes of magical information that she has stored in her mind. When Index happens upon Kamijo's life, she finds a loyal friend and protector in him, and despite the fact that Kamijo is easily the weakest kid in Academy City, he has something else going for him: the Imagine Breaker, an unexplainable power that is stored in his right hand and negates the powers of others. The Imagine Breaker will undoubtedly prove useful in this situation, but Kamijo's undying devotion to Index will be the most effective tool he possesses in the struggle to save her against the onslaught of scientists and sorcerers coming from all directions.