The mother-in-law, Hikari, who is more beautiful and busty than her daughter, moves in with her daughter's family. Hikari always stays close by, taking care of her daughter's household, but her son-in-law, Yuta, is so drawn to the allure Hikari exudes that he loses interest in having children. One night, as Yuta heads to the bathroom, he hears lewd noises coming from the bath. Peering slowly, he discovers Hikari indulging in self-pleasure. Excited, Yuta gazes at Hikari's seductive body, harboring a certain desire...