Aiju: Akai Kuchibiru (1981)

Naomi (Jun Izumi) and her business partner Tadashi run a neighborhood bar, sharing the profits, as well as each other. One evening, a yakuza gangster swaggers into the bar with a stack of money for Tadashi. he takes Naomi in an exchange. She is trained as a high-class hooker and is, seemingly, grateful for getting the opportunity to experience the joy of sex. However, appearances are deceiving. Secretly, Naomi is carrying grudge against the yakuza and she finally has the opportunity to take revenge.