Mizuha Miyama is a third-year student at Kitanohashi High School who holds several prominent leadership roles simultaneously: she is the head of the Manga Research Club, the student council president, and the representative of the school's cultural clubs. Her elevated status gives her an unusually strong presence within the school’s social hierarchy. She is a childhood friend of Takeo Takakura, the president of the Magic Club, but she treats him with relentless teasing and scolding, often singling him out as a target for her bossy and intimidating behavior. Her attitude toward him is confrontational, yet beneath the surface she harbors secret romantic feelings for him, which she expresses through her persistent bullying.

Mizuha’s personality is marked by a sharp contrast between her public authority and her emotional immaturity. She is openly snobbish and imperious, expecting deference from others, and she is known for using her physical appearance—particularly her large bust—to intimidate Takeo. Her own club members worship her, reinforcing her sense of superiority. However, her personal feelings often erupt in clumsy and undignified ways, revealing a less composed side. She is wealthy and enjoys a certain ojou-sama elegance, but she also acts as a bully and a tsundere figure, mixing harshness with hidden affection.

In the story, Mizuha serves as a supporting character. Her Manga Research Club is located next door to the Magic Club, and her frequent interactions with Takeo and the other club members provide much of the series’ comedic tension and romantic subtext. She does not possess any magical abilities; her influence relies on her authoritative positions and her forceful personality. Her motivation revolves around maintaining her control and her connection to Takeo, though she never openly acknowledges her deeper feelings for him. Over the course of the series, she shows little overt character development, but her hidden affection hints at a more vulnerable side that remains largely unexpressed.