Yûkai! Hitozuma gômon (1982)

Matsubara, a corrupt loan shark, has a wife, Yuki, who is a decade younger than him. He also has an abnormal relationship with Jiro, whom he uses as a kind of tutor. Jiro looks at Yuki with jealousy and lust as she goes on a rampage to find other men while her husband is away on business.