Saki's son, Yuuki, is invited by Yurika, the mother of his classmate Masaru, to go on a hot spring trip with two parents and children. In fact, Yuuki had long admired Yurika's beauty and sex appeal. At the inn, thanks to the mixed bathing hot spring, I witnessed the long-awaited naked body of Yurika. Yuuki, who doesn't cool down excitedly, sneaks into Yurika's bed and does it at night. And the unfaithful relationship between the two will be known by her mother, Saki, and Saki, who loves Yuuki, will also be in estrus.