Park Jimin's sister Park Jieun is a trainee in JYP Entertainment and she Is living with BTS because their parents died in a car accident 10 years ago. Jieun also grew up with Mark Tuan but she doesn't know about a secret that Mark kept for years. However, she have a huge crush on Kim Taehyung who is a member of BTS but she just could not confess to him. Jieun will debut soon but relationships and personal issue are getting in her way. Will she be able to overcome the obstacles and let her dreams come true?