Wife's younger sister - Immoral domestic voyeurism -

Motohashi, who runs an osteopathic clinic, and his wife, who has finally become pregnant, have begun to see his wife's younger sister, Miwako, frequently. Miwako's husband is away on his own, but for some reason she remains in Tokyo. Motohashi's heart is stirred by the fact that she, who until recently remained childish, has transformed into an adult woman. One day, when Motohashi went outside the clinic to take a breather, he found Miwako and the employee Takashi hugging each other. Curious, Motohashi borrows a surveillance camera and decides to take a peek into Miwako's daily life, but...