Yuka, who is married to a man much older than her, has had trouble getting along with her stepchild. One afternoon, her son peeks in on Yuka as she relaxes. When Yuka notices, her son tries to leave without a word, but she desperately stops him, saying, "We're family!" Secretly harboring lust for Yuka's large breasts, Yuka's son takes advantage of her lack of assertiveness and demands that he let him fondle them. Although confused, Yuka accepts, wanting to get closer to him. However, once he gets a taste for it, his son's demands gradually become more extreme...