One day, Satsuki is happy that her daughter has a boyfriend, and when she returns home after forgetting something, her daughter has brought her boyfriend, Okamoto. When I peeked into the room to see what was going on, it was the first time the two had sex and it didn't go well and it was awkward. Satsuki, who wants to support her daughter's love life, decides to become Okamoto's training ground so that she can gain confidence. However, Satsuki's plump body excites Okamoto more than he imagined. It was supposed to be just her bare thighs, but it crossed the line and her erect penis lost control like a runaway locomotive.