A slightly overweight man, lacking exercise, begins training with a female personal trainer. A few days later, when they meet up to start their workout, a woman named Tsuki appears, her massive breasts swaying with each step. The man tries hard to focus on his training, but he can't take his eyes off Tsuki's gorgeous figure, making it impossible to concentrate. Gradually, he develops feelings for her, and before long, his fantasies spiral out of control, leading to an unexpected turn of events.