After losing her husband, the mother raised her son alone, but he graduated and got a job. However, to celebrate his graduation, he asked for sex. At first, she thought it was a joke, but they ended up having a one-night stand. One day, her son's workplace moves far away, so the two of them go on a trip to a hot spring for the ceremony. She wants to hold her mother again... the forbidden love between mother and son. She knows this is wrong, but her son's serious gaze makes Hitomi lose her composure. Their tongues entwine, they lick each other's private parts, and they have sex many times on this forbidden incestuous hot spring trip.