Kasumi and her husband Satoshi are suddenly locked in a mysterious cage with three other men: Sagawa, who seems to know something, the smirking Machida, and Reiya. A voice orders everyone to have sex as a countdown begins. Pressured by the others, Kasumi and Satoshi try to perform in front of them, but the strange environment makes penetration difficult. Before they can recover, Sagawa and Machida attack, taking over in the challenge to make Kasumi climax a total of 100 times.