Her remarried husband is busy, and her stepson is a recluse... Yukari, who is happily united with the man she loves but feels lonely, witnesses her stepson Hiro masturbating. Unable to hide her excitement and agitation at his young, rock-hard cock, Yukari retreats to the bathroom to soothe herself by masturbating. Learning that her stepson's reclusion is due to him being "disliked by girls," Yukari decides to teach him about the female body, step by step, in order to overcome his trauma toward women. Having no sex with her husband, Yukari finds it amusing when her stepson awkwardly touches her, and eventually, as he leans forward to her, her feminine side is revealed. They unite with a bare penis, and Yukari finds her stepson's young, hard cock, thrusting frantically, irresistible. Hiro, who is engrossed in his newly discovered sexual experience, desires her, and Yukari rediscovers her femininity. "Who feels better, Dad or me?" "Hiro's dick is the best!" Driven by a sense of guilt towards her husband, mother and son devour each other's bodies day after day, crossing the line between parent and child in a forbidden act of incest...