A Certain Magical Index (To Aru Majutsu No Index) takes place in a world where science clarifies supernatural powers. Kamijou Touma is a resident student attending a school where the development of psychic abilities is just a part of the curriculum. While his magical level is 0 (powerless), his right hand contains the undetectable power of "Imagine Breaker", an ability that negates any and all supernatural powers, be it psychic, magical, or divine.
One day, he finds a young Anglican Nun lying across the railing of his dorm room's veranda. Her name is Index Librorum Prohibitorum, whose photographic memory has recorded 13,000 forbidden magical texts. While she is being chased by evil Magicians, she is also protected by the Walking Church (her nun's robes), made from a replica of the Shroud of Turin. However, Touma's Imagine Breaker accidently destroys these robes, and before he knows it, he is fighting the evil magicians and trying to protect her.