Nina has a boyfriend, her work is going well, and she seems to be living a happy life, but she's dissatisfied with her sex life. Her boyfriend has a low libido, and her proud figure is wasted every day. Then, her boss, Oshima, asks her for sex, and despite her reluctance, she opens her legs. She thought her relationship with her boss was just work, but her physical compatibility is excellent, and before she knows it, she cheats on him more and more, becoming a naughty woman. Late at night...