Following the first year high school student, Arisugawa Hikaru, comes a tale of Gaitou: a thief who only appears in dreams and steals the darkness inside of people's hearts. Hikaru, one of the Gaitou, hunts down Gai rabbits, one of the lower-class demons that seek the darkness in humans. With the aid of his companion, Ban, Hikaru protects people from falling into despair; however, the game has yet to begin.