トレーナーのセクハラレッスンに「私は人妻です！」と抵抗する彩だが、マッスルピストンに今まで味わった事のない絶頂を体験！特にバックピストンが強烈で、子宮をエグられるような快感に汗も潮も吹いて痙攣アクメ！旦那では1度もイケなかった巨乳妻が何度もイキ狂って、旦那以外の精液（プロテイン）を膣奥に注がれて理性崩壊！快楽に溺れた彩は、不安に思う旦那をよそに今日も寝取られにジムに通う。

Aya resists her trainer's sexually harassing lessons, saying, "I'm a married woman!", but the muscle piston gives her an orgasm like she's never felt before! The back piston is especially intense, and the pleasure of having her uterus gouged out makes her sweat and squirt as she convulses in ecstasy! The big-breasted wife who could never orgasm with her husband goes wild with pleasure again and again, and her sanity crumbles as semen (protein) other than her husband's is poured deep into her vagina! Drowning in pleasure, Aya goes to the gym again today to be cheated on, oblivious to her worried husband.