Minazuki Hikaru, a beautiful black-haired girl working in a quiet library, falls prey to the clutches of a gal couple in the confines of a commuter train. With her thighs pinned on both sides in a "double crab" position, she has no way to escape as they relentlessly attack her private parts. The vibrations of the shaking car and the warmth of other people transmitted through the fabric transform her sense of shame into pleasure. Every time a finger digs into her private parts, she trembles, trying to suppress her voice. This is a vivid record of the process in which a young girl is dragged to an unknown climax amid the extreme sense of immorality of public lesbian development.