Chisa Hoshino is a married woman neglected by her busy husband, leaving her sexually frustrated. One day, her husband's younger brother suddenly visits, taking advantage of her husband's absence and pressuring her into a physical relationship. Though shocked at first, her neglected, lustful body instinctively responds to his advances, and she gives in. From then on, the brother-in-law regularly visits whenever her husband is away. Though she knows it's wrong, Chisa continues the illicit affair. But one day, the brother-in-law stops coming. It's then that Chisa realizes someone else has been waiting for her. Her heart begins to waver, setting off an intense emotional and erotic turning point.