Do Hyun Joong, a fallen bodybuilding star, now manages a rundown 24-hour gym. Lee Mi Ran, fresh off a breakup, mistakes it for a nightclub and ends up humiliated. Hyun Joong offers to transform her life through intense training, but his brutal honesty drives her away. Still, his words hit a nerve. Can Hyun Joong change heartbroken Mi Ran's life and save the crumbling gym?

Mi Ran's intense training program falls apart and goes to waste after she breaks down in front of her ex-boyfriend. Despite achieving some results, including fitting into an undersized dress, Mi Ran quits the gym and demands a refund, leaving Hyun Joong frustrated. Meanwhile, Hyun Joong puts everything on the line to attract 120,000 new members to the gym, determined to turn the struggling gym around.