A married woman named Yukari attends a gym where she encounters a trainer who begins to sexually harass her during their workout sessions. Despite her protests that she is a housewife, he continues his advances until one day when he pushes her limits beyond anything she has ever experienced before - especially during back piston exercises which feel incredibly intense, causing her womb to contract violently around him while she cums uncontrollably multiple times! This experience leaves her completely spent and unable to think straight; filled with pleasure unlike any other time in her life as a wife. Embarrassed by this encounter but unable to resist its allure, Yukari decides not to tell her husband about what happened at the gym and instead returns there every day hoping for more opportunities for forbidden pleasure...
