Rieko, married to a man with a stepson, had been married for three months. She got along well with her husband, but her relationship with her son, Kazuki, was strained. At her husband's suggestion, they went on a hot spring trip, which became an opportunity to get closer to each other. However, Kazuki, feeling a surge of desire for Rieko, couldn't suppress it and made his move while she slept... Rieko experienced multiple orgasms and was completely immersed in pleasure during his intense and persistent thrusting. Faced with this perfect harmony that she could never experience with her husband, her body gradually became unable to resist the pleasure brought by his hard penis...