Bang Heeyeon is a cheerful 16 year old girl who has been living without her parents for almost seven years since they passed away. She has only one person in her life and that is non other than her brother, Bang Yongguk. Yongguk has been her everything he has tried his best to keep her safe and out of trouble and has always wanted the best for her. However there is one thing he can't handle, boys. He can't stand the idea of his little sister having a boyfriend. So what will happen when Heeyeon's heart falls for one of s, Zelo? How would Zelo react to all this? Would he accept her heart? Would his relationship with his leader be affected?