Sae divorced her husband and lives with her son. Her son doesn't make her, doesn't go out on holidays, just sleeps all day. Once in a while she would take her outside and invite her to a hot spring trip just the two of them. Her son, who has always loved her mother... Sae is puzzled by the sudden confession, but she loses her son's enthusiasm and opens her forbidden door with the promise "If it's just once...". It was a one-time promise to her, but before long, her swell of pleasure awakens Sae's female instincts...
