A world where madness has become commonplace with the passage of time. Bizarre crimes that defy human norms have reached the point where they can no longer be defined or judged by existing laws. We named them "Nonhumans." A situation in which neither prevention nor post-incident response is possible through conventional morality and ways of thinking. In the end, the system makes its final decision. "Monsters for monsters, Nonhumans for Nonhumans." Thus, a group of executioners more monstrous than the monsters themselves was born to hunt them down.