The story follows Arisugawa Hikaru, a first-year high school student, and introduces Gaitou: a thief who appears only in dreams to steal the darkness within people's hearts. Hikaru, a member of the Gaitou, hunts down Gai rabbits, lower-class demons that seek out darkness in humans. With the help of his companion, Ban, Hikaru protects people from falling into despair; however, the game has yet to begin.