Joutaro Fukamachi is a private investigator and has the motto of "Trouble is my business," which was inspired by the story of his idol Raymond Chandler. He dreams of being a second Philip Marlowe, but still has ways to go. His agency called Shark resides in the adjoining room of a dentist's office, and Joutaro's most fearsome weapon is the use of the strongest human muscle: his jaw. He bites his opponent and doesn't let go again.