In Academy City, scientists research the students with supernatural powers to help them develop. One student, Kamijo, encounters Index, a young nun fleeing from a sorcery society that covets the 103,000 volumes of magical knowledge stored in her memory. Although Kamijo is classified a level 0, Index finds him a faithful friend and protector, as he possess the "Imagine Breaker," an unexplainable power stored in his right hand that totally negates the supernatural powers of anyone.