Kodai accompanied his mother on a trip to a hot spring with his relatives. He meets up with his aunt Yumi and her friends at the inn, but his young cock can't control itself when he sees her voluptuous body after a long time... Captivated by his fully erect cock, Yumi releases her daily sexual desire that cannot be satisfied by her husband through him. Meanwhile, Kodai, who has discovered the joy of sex for the first time, continues to pursue Yumi with all his heart until the last minute before check-out. And she responds enthusiastically to his sex as he continues to fuck her like a monkey...