Toma Kamijo, a Level 0 student living in Academy City, has a unique ability that allows him to nullify psychic, magical, and divine powers, but it also negates his own good luck. Said power allows him to survive a reluctant duel against Mikoto Misaka, a powerful Level 5 psychic capable of controlling and generating electricity, ending with Mikoto causing a citywide blackout. The next morning, Toma wakes up to find a young nun from the Church of England hanging off his balcony. Introducing herself as Index, she reveals that she is being chased by magicians because she 'has' 103,000 grimoires. The two become friends after an embarrassing incident (involving Index proving the existence of magic and Toma proving the power of his right hand) and they part ways. However, when he returns home, Toma finds Index laying on the ground bleeding and, behind him, a man who calls himself a magician.