Obsessed with the perverse thrills of the mysterious Midnight Sleazy Train, Takumi accidentally boards the illicit vessel only to witness the public degradation of a student named Karin. Refusing to participate with someone already "claimed," Takumi seeks a way to return on his own terms. He is eventually informed by a mysterious figure that the only way to secure passage is to scout and deliver a new "sacrificial lamb" to serve the train's passengers.
To gain membership on the exclusive Sleazy Train, Tamura targets the stunning and aloof Ms. Kamijo of Hakuou Academy. With the assistance of the legendary operator Tetsuo Amano, the proud woman is lured onto the train, where she quickly abandons her inhibitions to indulge in hedonistic pleasure with the passengers.
Takumi continues his role as a recruiter for the clandestine "Sleazy Train," manipulating a university student and a housewife to satisfy the organization's desires. After narrowly escaping a sting operation with the help of his colleague Kyoko, Takumi begins to uncover the dark truth about his employers. He eventually realizes that he is a mere pawn in a larger game and that Kyoko is actually spying on him for the organization.