Jeongyeon falls for a popular girl, a girl chased by many boys, a girl that Jeongyeon knows she’ll never get. Until... she faces herself and confesses, which inevitably leads to her rejection. And something else.

A mysterious Blue Note signaled the change of everything, a simple Blue Note managed to change their future. Jeongyeon and Chaeyoung both have secrets that need to keep locked inside them. And somehow, Nayeon gets entangled with their fates.