Recently, a trendy dark gym opened on the street where the Hojo couple lives. Maki decided to start going there right away for stress relief, but the reality of the dark fitness was that it was an evil gym that put sensitivity-enhancing drugs in the ladies' drinks. On the first day, Mapi was quickly drugged and the effects were amazing. Mistaking her increased libido for a result of exercise, Mapi returns home to seduce her husband, but he's too tired from work to even look at her. Then, unaware of anything, Mapi visits the dark gym again, and evil hands pounce on her…
