Shota is going on a hot spring trip with his mom's friend Yumi, her husband, and his own parents. With both sets of parents present, Shota must sneak around to avoid getting caught. He sets his sights on Yumi's big breasts and begins pulling various naughty pranks on her. Kind-hearted Yumi gently tolerates his mischievous advances with a smile. In the car, he fondles her large breasts, thrilling in their secret. Later, they bathe together, scrubbing each other clean. Evading the watchful eyes of the adults, Shota and Yumi eventually take their relationship to an outrageous level!