Kiriko lives with her husband and son, Koichi. The reason for her long and successful marriage is, quite frankly, "sex." Her husband fulfills Kiriko's sexual desires almost every day. But then, one day, her husband goes on a business trip. What's worse, the timing is that Kiriko's period is just a few days away. Kiriko has always been worried about her abnormally high sexual desire before her period. So, when a delivery man comes to her house, Kiriko makes a move on him...