Aika Miura: Groper Train Ecstasy (2001)

Tsuruta, a Tokyo government worker with a habit of unwanted touching, receives a note from a woman who asks him to contact her. He suspects a trap and ignores it, but the woman, Eiko, begins following him. She eventually confronts him. Eiko asks Tsuruta to help Seiichi, the heir to a wealthy family, with a study on sexual crimes and culture. Seiichi wants to understand the practice of groping and begins shadowing Tsuruta on the train. As Seiichi practices, Tsuruta becomes drawn to Eiko, but Seiichi's actions take a dangerous turn.