In this world, villains and heroes exist. Villains use their powers to cause terror and crime, throwing society into chaos. In response, a hero organization called the Quack-Quack Expedition Team was established. Villains are classified into seven ranks: S, A, B, C, D, E, and F. Captured villains are usually interrogated before a decision is made on their execution. S-rank villains are almost always sentenced to death.