Natsuzora Rika plays a serious, trusted college swim-team leader with a toned waist, round ass, and powerful thighs. While training to qualify for the national team, she develops pain in her lower back and asks her coach for help. The therapist he recommends is secretly working with him on a planned assault. What begins as a normal massage turns sexual as drugged oil sends her libido and sensitivity soaring. She becomes hooked on the therapist's experienced, obscene touch, is conditioned into total obedience, and is dressed in an extreme modified racing swimsuit. Despite having a boyfriend, she repeatedly cheats through session after session of sex, her once-pristine image destroyed as she sinks into a cycle of degradation and pleasure.