Natural High presents an explicit documentary-style film following women who become aroused by molestation on crowded trains, secretly filmed along the famous Yamanote Line. As the stimulation intensifies inside the train, their reactions grow increasingly passionate, captured in intensely erotic moments. Even after filming ends, their arousal doesn't subside—leading to masturbation in public restrooms and visits to adult film actors' homes for wild, uninhibited sex. The story plunges deeper with escalating, graphic scenes, including cowgirl positions, threesomes, and more, showcasing the hidden desires of married women. Starring Nao Mizuki and Kazuha Mirei.