Miharu Shimizu is a supporting character who appears later as a minor antagonist in the series. She is a second-year student at Fumizuki Academy and serves as the Ambassador for Class 2-D. She has a cute appearance with pumpkin orange hair that is styled into ringlet pigtails and yellow eyes. Miharu's background centers on her placement in the middle-ranked Class D, a position that gives her a degree of authority as the class ambassador but also places her outside the main conflict between the lowest class and the elite class.

Her personality is defined by an intense and possessive infatuation with Minami Shimada, a girl from Class F. Miharu refers to Minami as Minami onee-sama and is relentless in following her around the school. She becomes hostile and physically aggressive toward Akihisa Yoshii whenever he appears to get too close to Minami, viewing him as a rival for her affection. This obsession drives most of her actions and interactions. Her primary motivation is to be close to Minami and to protect her from what she perceives as threats, especially from male classmates. She is so devoted that she does not mind being forced to take remedial classes as long as she can remain with Minami.

In the story, Miharu functions as an obstacle and a source of comic conflict, particularly in episodes involving interactions between Class F and Class D. Her role expands from a background student into a more active antagonist during class battles, where she uses her position as class ambassador to challenge the protagonists. Her key relationship is with Minami Shimada, whom she idolizes. She also has a contentious relationship with Akihisa Yoshii, whom she attacks whenever he gets too close to Minami. Her relationships with other characters are largely defined by this central fixation.

In terms of development, Miharu remains largely static throughout the series. Her obsession with Minami does not diminish, and she does not undergo a significant personal transformation. She continues to act as a minor antagonist and comedic foil. Her notable abilities are tied to her role as Class D Ambassador, which gives her authority to initiate and participate in Summoner Test Wars. In battle, her summoned beast's strength reflects her academic test scores, though the series does not highlight her as an exceptionally powerful combatant. Her persistence in pursuing Minami and her willingness to use her official role to interfere with the main characters make her a memorable supporting figure, but she does not receive substantial character growth across the story.