Son Jaesoo, a young girl, sister to the leader of the famous boy group Monsta X. She is a rookie actress and a model. As close as she is with her brother, she made a new family with the others Monsta X members. But one thing she didn't know at all, was that how much her life changed after meeting Monsta X and after becoming a bigger actress, and meet her ex boyfriend that she haven't met in months and who are her brothers close friend.