Turning 30, Taro became concerned about the fat accumulating around his abdomen. On his older brother's recommendation, he asked his sister-in-law, Ayuka, to become his personal trainer. On the first day of training, during Ayuka's careful stretching exercises, Taro couldn't help but get an erection beneath his workout clothes. However, Ayuka pretends not to notice and ignores it. A few days later, the two continue their training, drenched in sweat. While Ayuka's coaching gradually transforms Taro's body, an unexpected turn of events begins to unfold between them.