Goo Jae-hee (Sulli), a Korean girl who lives in the United States. She is bullied in school due to her looks and almost wanted to drop out of school. One day, she sees a track and field competition on TV, and becomes attracted to one of the high jump competitors, Kang Tae-joon (Choi Min-ho). She begins to idolize the young athlete, and is then inspired to join in sports and to stand up against her foes. She eventually transfers to Korea to attend the same school that Tae-joon attends after he suffers an accident that could potentially end his career. There is a catch, however: Tae-joon attends an all-boys high school, Genie High School, so Jae-hee cuts her hair short and disguised herself as a boy to enter the school.
