Hae Na and Seungho were childhood sweethearts. However, at the age of 8 , Hae Na's family decided to migrate to the US. After many years, she finally returned to study in Korea while her parents are still in the US managing their business. She had not forgotten about Seungho and came back just to fufill the Promise, but, Seungho had moved house and she didn't know where he was. Well, that was until she enrolled in CheongShim High School, and met him and his girlfriend...?