Yoshikazu is on a hot spring trip with his mother and relatives in place of his father, who is at work. He can't help but stare at his aunt Mariko, whom he hasn't seen in a long time, and her unconscious eroticism... Mariko sees him in agony. Captivated by his strong cock, Mariko uses it to release her daily sexual desire, which her husband alone can't satisfy. Having discovered the joys of sex through her, Yoshikazu continues to devour her like a monkey, and...