After losing her husband at an early age, Ryouko devoted herself to raising her only son. One day, the boy came home in tears after being bullied for having a drawn-on pussy mark on his body. Feeling deeply for him, Ryouko decided to take on the role of his father and began teaching him about sex using her own body. Her son's curiosity grew uncontrollably, and before long, she allowed him to penetrate her. Though she felt guilty as a mother, she could no longer suppress her own growing attraction to her son's cock.