Two trainees who have been inseparable since childhood begin a secret romance after a spontaneous kiss during intense dance practice. As their relationship deepens, their long-awaited group debut is finally confirmed. But just before debut, the company imposes a strict no-dating rule, forcing them into a painful breakup. Yet even after separating, one of them remains affectionate and possessive toward his ex. With their unresolved feelings hidden behind the idol spotlight, can they survive working together as ex-boyfriends?