Love Beast: Flower of Vice (1981)

A woman and her business partner run a neighborhood bar. He hopes they can be married someday. One evening, a yakuza swaggers into the bar and asks the woman how much would it take to have sex with her. She jokingly replies “A million”. With that the yakuza pulls out a huge wad of bills, kidnaps her and viciously trains her to be a high class call girl. She soon begins to enjoy the training and starts to attract big clients and big money. But secretly she waits for her chance to take revenge on the man who forced her into this life of sin.