Yoshiki Tsujinaka's best friend, Hikaru Indou, went missing in the mountains six months ago and returned with no memory of what happened. Yoshiki is convinced that the person who came back is not the Hikaru he knows, and when he confronts Hikaru, the latter reveals a monstrous form. This entity, who claims to be the real Hikaru, begs Yoshiki to keep its true nature a secret, fearing it may harm him. Despite its supernatural side, the creature displays a childlike innocence, eager to experience human life for the first time.