Toshiko Fujimi, a 51-year-old housewife, lives alone every day while her husband is away on a work assignment. Overcome by loneliness, she masturbates late into the night, moaning as she pleasures her mature body. One day, her son Masaru accidentally catches her in the act. Shocked and aroused, Masaru looks down at his own erect penis. Seeing this, Toshiko feels both shame and attraction, and impulsively takes her son's cock into her mouth.