O-chou sits in a jail cell after confessing to slaughtering her husband's entire family, a crime she claims to have committed to escape years of abuse for failing to please them. The wandering medicine seller known as Kusuriuri doubts her story and comes to question her directly, only to find a masked Ayakashi already circling her cell, and begins tracing the Shape, Truth, and Reason of the Nopperabou behind the killings.