Located in the American Area 51 is a society inhabited by a diverse array of supernatural beings—including kappa, vampires, aliens, deities from various mythologies, and mythological figures such as King Arthur—as well as others. Alongside these non-humans lives a population of humans who, for one reason or another, cannot survive in the ordinary world. Among them is Magoi Tokuko, commonly known as McCoy, a tough woman who handles cases with the aid of her kappa associate, her extensive knowledge of the area, and her pistol. Operating from an office she has established in an unfinished subway station, she accepts a wide variety of jobs (such as recovering stolen goods or infiltration) from the many humans and non-humans who pay for her services.