In Academy city, a place wholly constructed for the purpose of creating and researching psychic powers. A boy, without even a trace of psychic power of his own, finds an English nun hanging from the rail of his balcony, overcome by hunger. The nun introduces herself as Index and discloses the existence of magic and a secret power struggle between Academy city on the side of science and the Christian church on the side of magic. The boy who seemingly can't get any powers of his own, do have one thing that can influence the tides in the struggle and everyday life in a city where power is everything, a hand that cancels out all powers, psychic and magical alike.