Minatozuki Sana is a peppy and aspiring 20 year old Japanese girl who dreams becoming a famous lyricist.Growing up on her own in Korea, living in a small  apartment alone. After a tragic accident of her parents, she was force to put into an adoption for a year and she was lucky that she got adopted by a Korean couple,married for 20 years without a son or a daughter.

They entrusted her to live by her own when she turned 20 despite she is looking for a job. Little did she came across to a music entertainment company, BigHit Entertainment. After the interview, she passed and the CEO give her a shot of writing a new song for his boy group, BTS.

When the boys met Sana, they immediately liked her despite her charming look. Soon after, they got closer and they make a bet who will capture her heart.