Sae divorced her husband and lived with her son. My son doesn't have a girlfriend, he doesn't go out on holidays, he just sleeps all day. Occasionally, I invite him on a hot spring trip just so the two of us can take him out. A son who always loved his mother... Sae was confused by his sudden confession, but he gave in to his son's enthusiasm and opened the forbidden door with the promise "If just one time...". It was only a one-time promise, but in the end the surging pleasure awakened Sae's womanly instincts...