Ryouko, driven to her limit by a sexless marriage, one day enters her son's room to check on his studies and catches him engrossed in masturbation. At that moment, she sees his enormous erection—far beyond anything she imagined—and her pent-up sexual frustration surges uncontrollably, clouding her mind completely. Losing all composure, Ryouko instinctively positions herself over her sleeping son's genitals and, overcome by impulse, begins thrusting against him.