Ryoko has not had sex with her husband for a while and her sexual frustration is on the verge of exploding. One day, when Ryoko opens the door to her son's room to check on him studying, she witnesses him masturbating enthusiastically. The sight of his erect penis, which is much larger than she had imagined, intensifies her sexual stress, and she loses control of everything and finally jumps on her sleeping son's penis...