Chul-soo is a twelve-year-old boy who attends an acting training course. One day, the teacher arranges for him to rehearse a "love confession" scene with the prettiest girl in class, Yeon-hee, but he is unable to perfectly portray the feeling of his heart pounding. However, when his acting counterpart gets replaced with Soo-hyun, a male classmate, Chul-soo realizes that some emotions don't need to be rehearsed...