Her friend's father disappeared and she had no children, so she took in one of the twins that her friend gave birth to. Her son grew up and went on to college. When her son applied for a passport to study abroad, he found out who his real parents were. At her friend's suggestion, Hibiki went on a trip with her son to talk calmly. Her son learned that they were not related by blood and thought of his adoptive mother as a woman. At the hot springs, the son gets an erection from his beautiful mother's beauty and takes Hibiki's hand and strokes it. Hibiki naturally takes it in her mouth... A story of incest between step-parents and step-son, who are freed from reason and taboos and give themselves over to pleasure. Free trial points available for the first time!