Cleavens is an international flight attendant blessed with a rare beauty. Twenty years ago, she made a promise to the boy she had met during the night of a summer festival. Now, all she has is a lockable pendant, which can be unlocked with a key that the boy bestowed before they had separated their ways. Years had passed but she's still holding on to their promise even there's no guarantee, hoping that one day they will reunite. However, when their company went bankrupt she was forced to marry Haru, a narcissist guy who loves to bully her.