Yoshikazu is on a hot spring trip with his mother and relatives in place of his father, who is at work. He can't take his eyes off his aunt Mariko, whom he hasn't seen in a long time, for her unconscious eroticism... Mariko sees him in agony. Captivated by his strong cock, Mariko uses it to release her daily sexual desire, which cannot be satisfied by her husband alone. Having discovered the joy of sex through her, Yoshikazu continues to devour her with the fervor of a monkey, and in response, Mariko loses herself and shakes her hips wildly...