Yang Kyungmi and Kim Kibum (or as he likes to be known as – Key) have been friends for a while. Not like childhood friends that have known each other since they were in diapers or friends from elementary or middle or high school. They’re just friends that met at events from other friends. But things start to change when Key breaks up with his girlfriend, Kyungmi's younger sister, Sooyun. In his attempt to try and win Sooyun back he discovers somethings. Was he in love with Sooyun?