Mizuki seeks honesty and stability in men. That's why she's dating Seiji, a good-looking, capable colleague with a promising future. But she's dissatisfied with the sex they have. Meanwhile, her best friend Anna is looking for excitement in a man. The two meet Keisuke, a slot machine pro. Anna falls head over heels for the handsome Keisuke, and they soon become involved. Mizuki is wary of Keisuke at first, but when her relationship with Seiji becomes strained, she ends up having sex with him. Mizuki and Anna have a falling out. Then Keisuke's former girlfriend shows up, and the situation develops into a battle between three women. A man is at stake in a slot machine game, but who will win Keisuke?