One day, while Maki Hojo was doing the dishes at home, her neighbor's wife came over and started chatting. Behind her stood Maki's son, Shingo, for some reason. The neighbor explained that she had just caught Shingo trying to take off his underwear and had scolded him. Since they were close, the situation was defused, but Maki felt troubled by her son's behavior. She realized he had already reached the age where he was becoming interested in women. With her husband away on overseas assignment, Maki made the decision to personally guide Shingo's sex education—using her own body.