Even though she has finished raising her children, Reiko and her husband are still on good terms. To her son, his friends say that he envies his mother for being young. One day, the son peeks at Reiko and her husband having sex at night, and finds his mother sexy, which makes him aroused. That night, while his father is out, the son talks to Reiko. "I got excited watching you having sex with your father," the son says, and attacks Reiko. Reiko desperately tries to escape, but she is no match for her adult son and ends up being raped. What's more, she is already feeling it with her son's rod...