Mizuki Ashiya is a Japanese-American girl who went to all boys school, and dress as a boy. Just to meet Izumi Sano, her crush and an high jumper. Later Sano found out she was a girl and kept it a secret, because he like her too. Nakatsu also likes her too but he thought that he was gay beacause mizuki is a "guy".
Mizuki Ashiya (芦屋 瑞希 Ashiya Mizuki) is the heroine in the shōjo manga Hana-Kimi (Hanazakari no Kimitachi e), by manga-ka Hisaya Nakajo.
Mizuki Ashiya, who was born in California to Japanese-born parents, is the heroine of the story. She spontaneously moved from California to Japan and enrolled into an all boys school (Osaka Gakuen) because her idol, Sano Izumi, who’s a top high jumper and the same age as her, attends the school. To look like a boy, she keeps her hair short and ruffled and wears a tight demin vest to hide her chest. In many ways, it’s good that she has a pretty flat chest, but she wants more cleavage between them. She’s a very fast runner (due to her mother’s athleticism), but is very clumsy at times (due to her father’s clumsiness). She is fluent in English and spoken Japanese, but her knowledge of written Japanese is initially below that of native Japanese her age. Mizuki loves all kinds of food, especially sweet things, which is a strong contrast to Izumi's dislike of them. Also, she can be quite stingy when it comes to sharing her food. She’s also a lover of animals, as one can see when she’s with Yujirou, Sano’s dog.
While in Japan, she lives in the same dorm room as Sano. There, she meets Shuichi Nakatsu, a talented soccer player who becomes her friend and later falls in love with her feminine side, leading him to think that he is gay. Other friends of hers are Senri Nakao, a "cute" boy (bishōnen) with a crush on the dorm leader, Minami Nanba, Sekime and Noe, two girl-obsessed, but good-hearted boys, Kayashima, a yoga-practicing boy with extra-sensory perception who can see ghosts and spirits, and Hokuto Umeda, the homosexual school doctor who helps her out. He knows that Mizuki is a girl but he helps her out on her love problems as well.
Even though Mizuki puts forth much effort to hide her female identity, Dr. Umeda and Sano separately discover her secret soon after she begins attending Osaka Gakuen. However, neither report her; Dr. Umeda judges her reasons as acceptable, and Sano conceals his knowledge for the sake of keeping Mizuki at the school. Although Nakatsu never gains the knowledge that Mizuki is female until the secret's out in the open, he perceives her femininity and becomes attracted to her, instead thinking that he himself is gay.
However, towards the end of her second year (and the series), the three student heads of the dormitories found out about her true identity. Although they tried to suppress the news themselves, in the end, Mizuki decided to leave Osaka. All was not lost though; during their university days, Sano finally proposed to her, and she accepted.