Yuri, the busty mother-in-law, has the same birthday as her daughter-in-law. Her son-in-law, Yoshinobu, sends Yuri the erotic underwear that he was supposed to give to his daughter-in-law. When he sees Yuri masturbating while wearing the underwear, Yoshinobu's desire is unstoppable. "You're probably sexually frustrated, aren't you, mother-in-law..." Yoshinobu relentlessly pursues Yuri's busty breasts everywhere, trying not to be found by the family...