Su-in is rejected when he confesses his feelings because he's considered "anchovy-thin." Seon-hee is dumped by Jae-hyeon, a player, because she's overweight. Young people dreaming of a life turnaround and a major change gather at a gym! Su-in and Seon-hee pretend to be a couple to take advantage of a couple's discount and sign up for the gym. Can they level up their bodies and minds for a better tomorrow? A fresh coming-of-age romance filled with sweat and passion unfolds at the gym!