At first glance, Fukuoka seems like a peaceful city, but under the surface, crime is running rampant. The city's Hakata ward is home to the professionals of the underworld: professional killers, detectives, informants, professional revenge seekers, those skilled in torture, and more. And according to urban legend, even a "killer of professional killers" exists in the city. When stories of the men in the underworld are told, a "professional killer murder" appears.