Motohashi, who runs an osteopathic clinic, and his wife, who is finally pregnant, have been seeing Miwako, his wife's younger sister, frequently.Miwako's husband is away from home, but for some reason she remained in Tokyo.Motohashi's heart flutters at the fact that she, who had been young until recently, has transformed into an adult woman.One day, when Motohashi went out of the clinic to take a break, Miwako and her employee Takashi were hugging each other.Intrigued, Motohashi borrows a surveillance camera and decides to take a peek at Miwako's daily life.