In the Edo era, Ichitarou, who runs Nagasakiya in Nihonbashi, has been ill since birth and can't leave his home. Despite this, he has demons like Shirasawa and Inugami guarding him at all times. One night, Ichitarou sneaks out and witnesses a murder. Following this event, there are multiple murders in Edo. With the help of his demons, Ichitarou starts looking for the killer.