Momoko has been living a lonely life since her husband was transferred away from home, but her daughter and son-in-law have returned home temporarily. Momoko's son-in-law Kimihiko, who was reserved at first, joins her and they spend lively and fun days together, but one day Kimihiko falls ill and she has to take care of him... Touched by his mother-in-law's kindness, Kimihiko begins to see her as a woman, and they end up entering into a forbidden relationship. The two live under the same roof. Before they know it, their sense of immorality turns into pleasure...