Hana-Kimi centers around Mizuki Ashiya, a Japanese girl who lives in the United States. One day, she sees a track and field competition on TV, and becomes attracted to one of the high jump competitors, Izumi Sano. She begins to idolize the young athlete and eventually transfers to Japan to attend the same school that Sano attends. There is a catch, however -- Sano attends an all-boys high school, named Osaka Gakuen, and Mizuki must disguise herself as a boy to enter. The majority of the series happens during Mizuki's second year at Osaka (from Volume 4 onwards), although her first year was significant for her being able to remain in Osaka.