His wife's younger sister has come to Tokyo to live with them. She does yoga and is extremely flexible. She has a cute, devilish face and is flexible in erotic poses. If he were to penetrate her, it would surely feel good. While he was fantasizing about this, one day, he is molested and raped by a beast of the city, and his heart is broken. He intended to comfort her, but the two end up in a deep relationship, and the brother-in-law becomes immersed in his sister's young body, as her hole tightens to the point of death, without telling his sister.