Two years ago, Reina's husband began suffering from erectile dysfunction, and since then, their sex life has completely stopped. Having reached her limit, one day Reina accidentally catches her son Ataru masturbating. Overwhelmed by the sight of her son's impressive erection, she loses her composure and gives in to temptation, seducing him. Though initially hesitant, Ataru is drawn to Reina's mature allure, and the two embark on a forbidden relationship. However, Reina's intense sexual desire gradually affects her son's emotions as well, turning their affair into something more than temporary—a deep, inseparable bond.