Kei married a man with a child and became a full-time housewife. Her son Makoto witnessed his mother's affair when he was young, which caused him to distrust women and he would never open Kokoro to his stepmother Kei. One day, when Makoto secretly washed his underwear after a wet dream in the bathroom, Kei gently wrapped his penis around it and washed it, telling him, "It's normal for a healthy boy, it's not dirty at all." From then on, Kei began her own sex education, risking her life to teach Makoto, who hates women, the wonders of the opposite sex...