Koudai joins his mother on a family hot-spring trip and reunites with his aunt Yumi at the inn. Her voluptuous body makes the adult virgin instantly hard, and Yumi is captivated by his thick, swollen cock. Sexually frustrated because her husband cannot satisfy her, she uses Koudai to indulge every pent-up desire. Having discovered sexual pleasure for the first time, he keeps demanding her until the last possible moment before checkout, while Yumi eagerly matches his relentless pace through repeated sex and creampies.