" I'm sorry for leaving you but don't worry, I'll always be in your heart. "

Soojung and Baekhyun are best friends since they were born. Their parents were best friends, too. When Soojung was 15, she and her family went to a family trip. On their way home, they were involved in an accident. Only Soojung was safe. Soojung got injured at her right leg and her head. She was really sad at first because she lost her beloved parents and sister. But Baekhyun always by her side, cheering her up. She asked Baekhyun to promise that he'll always be by her side so does her. But Baekhyun couldn't promise. He couldn't be by her side forever. He's going to follow Soojung's parents.