Kim Seokjin, the oldest of the K-POP group BTS has a little sister who apparently hates him. When BTS takes a vacation in Jin's families summer house at the same time as his sister they know that they have to do something. They always heard their hyung cry to sleep and he always told them about how he missed his little baby sister. In three months can BTS find what made Jins sisters heart change and can they bring the sweet girl back.