Manami, the protagonist, is diligently training every day for an upcoming marathon. When her two friends find out, they begin "helping" her with her training, but their assistance quickly turns into repeated sexual harassment. Posing as stretch assistants, they grope and massage her 90cm G-cup explosive breasts and touch her groin under the guise of physical therapy. They escalate by making her ride an exercise bike completely naked, and even engage in sex under the pretense of improving her physical performance. As these bizarre situations continue, Manami becomes increasingly confused.