A couple takes part in a secret monitoring show where the girlfriend is completely unaware that her boyfriend is watching from just 30cm away. As a stranger approaches with the challenge — one million yen if he can watch her give in to another man until the end — the big-breasted amateur begins to respond to an arousal she cannot suppress. Her body reacts to a penis far larger than her boyfriend's, and despite her partner watching every moment, she becomes increasingly overwhelmed by the experience.