G-Spot Express exploits female masturbation throughout the story, commonly done by the male characters. The main story however, revolves around a jobless young man known as Katsuhiko, often referred to in the show as a “groper”. When not in his gloomy apartment, he travels from one subway station to the next on a regular basis at his leisure, scouting for women and fondling their body parts to a certain extent. One of the days, his “skills” were noticed by an old man, who partakes on this sexual harassment himself, together with a group of men that provide assistance and coverage for one another. Together with the old man, Katsuhiko continues to hunt down frail, innocent yet horny women on the express train.