Yumi, an education mom obsessed with academic pedigree, is eager to enroll her son Yoichi in the same prestigious school as his father. She's flawless in every way, but during her once-a-month dangerous days, her body becomes hypersensitive and she can't control her arousal. Yoichi secretly notices this and, to vent his daily frustrations, he casually masturbates in front of her on these dangerous days… With her husband away on business and having gone without sex for so long, Yumi, regardless of whether it's her son or not, eagerly devours the erect penis, moving her hips lewdly as instinct takes over…
