As Koichi hits puberty, he begins to become interested in his mother, Sachie's, big breasts. Every day, her big breasts sway before his eyes... Before he knew it, he wanted to not only look at them, but also touch them. One day, while Sachie is taking a bath, Koichi applies bubbles all over her body, saying, "I'll give you a body wash beauty treatment," and begins to rub her breasts and buttocks under the pretense of a massage. Before long, Sachie, who has been feeling good under her son's hands, becomes obsessed with the obscene charms of the bubble massage...