This story is just like a usual story that starts with 2 young childhood friends which start develop their feelings secretly to each other,will they be together at the end? ForewordIm YoonAh _ Kim Yoona-sweet,cute,caring-childhood friend of Sungmin-daughter for Taeyeon and Kangin Lee SungMin_Choi SungMin-handsome,caring,smart,good in sport-childhood friend of Yoona-confuse about his own feelings-son for Siwon and Tiffany Kim JoonWoon/Yesung _Kim Yesung-a popular boy in the school,good looking,nice,rich-likes Yoona as a sister or more than that...?-cousin for Lee Sunny Kim TaeYeon_Kim TaeYeon-mother for Yoona,wife for Kangin-cares about her husband and yoona alot,nice Kim YoungWoon/Kangin_Kim Kangin-father for Yoona,husband for Taeyeon-a hardworking businessman,loves his famiy Choi SiWon_Choi SiWon-father for Sungmin,husband for Tiffany-a strong man,likes to joke,business partner of Kangin Tiffany Hwang Mi Young_Choi Fany-mother for Sungmin,wife for Siwon-sweet,act Yoona like her own child-Dislike Sunny Lee Sun Kyu/Sunny_Kim Sunny-cousin for Yesung-Likes Sungmin-Flirty,evil,hate Yoona Jessica Jung Soo Yeon_Jung Sica (appear almost the end)-ex girlfriend of Sungmin-leaving Sungmin for some reason