A mother who has devoted herself to raising her son and lived a life without men, goes on a hot spring trip with her son and feels a sense of manliness when she sees her grown-up son naked for the first time in a long time! The son has also seen his mother as a woman since he was a child. The two of them become more open-minded and end up having a physical relationship on the hot spring trip. A story of incest between a mother-complex young man who gets an erection when he sees his mother's naked body and a sexually-driven mother who gets excited when she sees his erect penis.