Mizuki Ashiya is the female protagonist of Hana-Kimi, a Japanese-American girl who moves from the United States to Japan to enroll in the all-boys Osaka Gakuen under a male disguise. Her motivation stems from seeing high jumper Izumi Sano on television during a track and field competition; inspired by his performance, she idolizes him and later learns he has quit the sport. Determined to meet him and help him return to high jumping, she cuts her hair short, binds her chest, and convinces her parents to let her transfer. The school doctor, Hokuto Umeda, and Sano himself discover her secret early on: Umeda agrees to keep it after hearing her reasons, while Sano discreetly helps her maintain the disguise. Her cheerful and energetic personality is central to the story, expressed in a straightforward and honest manner. She is a versatile athlete, particularly a fast runner, though she inherits a degree of clumsiness from her father. She loves animals, sweets, and is known to be stingy when it comes to sharing food. Throughout the series, Mizuki navigates the complications of living in a boys’ dormitory while hiding her gender, forming close bonds with her roommates Sano and Shuichi Nakatsu. Nakatsu, unaware she is a girl, develops romantic feelings for her, leading him to believe he is gay. Mizuki’s relationship with Sano evolves from admiration to deep friendship and romantic tension, helping him rediscover his passion for high jump. Her interactions with other students, such as the perceptive and ESP-gifted Taiki Kayashima, the dorm leader Minami Nanba, and the flamboyant Tomoya Sekime, highlight her adaptability and sincerity. Over the course of her journey, Mizuki grows from a starstruck fan into a more self-aware individual who must confront her own feelings and the consequences of her disguise. Her arc culminates in her secret being exposed and her eventual decision to leave the school, though she and Sano later reconnect during their university years. Notable abilities include her athleticism, especially in running, and her fluency in English and spoken Japanese, though her written Japanese is initially below native level.