Mitsui Kota, an unremarkable high school student, joins his school's fishing club at the invitation of his best friend, Uchi Shinjiro. He soon discovers that the club is a front for a vigilante organization called Spinner Bait, which operates under the control of the yakuza and uses methods that border on extortion to crack down on crime. The group maintains a strict internal hierarchy based on points earned for each operation, but Mitsui remains stuck at zero points, living a frustrated and stagnant existence. As he struggles to find his place in this morally ambiguous group, a series of murders begins to shake the town. Mitsui's life takes a dramatic turn when a mysterious man approaches him, claiming to have found the killer's notebook, pulling him deeper into a web of violence, suspicion, and psychological tension.