A mother who devoted herself to raising her son and lived a life without a man, felt a man in the nakedness of her grown son for the first time in a long time on a hot spring trip with her mother and child!And her son also saw her mother as a woman from childhood.On a hot spring trip where such two people became open, they had a physical relationship.An incestuous story about a mother's boy who gets an erection when he sees his mother's naked body and a mother who gets excited when she sees her erect cock.