Heigoro Saito, the clerk of the Kitamachi magistrate's office, has a hidden side. A "demon slayer" who guides demons who cannot be judged by law to the Sanzu River. Heigoro used to terrify villains as a "human slayer". Beneath the mask of justice, he was intoxicated with the taste of killing people. However, the blade killed his wife, and Heigoro stopped drawing his sword. But... the cries of regret from the oppressed make Heigoro draw his sword again. Heigoro swings his sword. While he suffers from the work of killing people...