Heechul is a rich guy who went to live in america in his childhood and cameback to korea again because of his work , he had a bestfriend online ,Kibum , they met in Korea , and started working together, Kibum has two sisters , Tiffany and Yoona , Heechul knew Yoona who is kibum's sister , then they fell for each other by the time, will their relationship work with Kibum ? his best friend with his sister?