While Fukuoka city appears tranquil at first sight, a scourge of crime lurks beneath its surface. The city's Hakata ward harbors a host of underworld professionals, including hitmen, detectives, informants, vengeful personnel, and proficient torturers. Additionally, an urban myth asserts the existence of an assassin who preys on fellow assassins. Whenever tales of these shadowy figures circulate, whispers of the so-called "professional killer murder" begin to materialize.