Ten years have passed since a mysterious wall cut off a portion of Tokyo from the rest of the city. "Hell's Gate" is the name of the impassable area. Since then, "Contractors'" existence has come to light. They appear to observers to be murderers with remarkable talents. Misaki Kirihara, a police officer, is tasked with putting an end to the awful acts. Li Shengshun, who presents herself as a friendly exchange student, actually works for an unidentified group whose objectives are unknown but differ from those of the police.
