Miharu Shimizu serves as the ambassador for Class 2-D at Fumizuki Academy. She possesses pumpkin-orange hair styled in ringlet pigtails secured with black X-like bows and topaz-colored eyes, projecting an exaggeratedly girlish image that starkly contrasts with her conduct.

Miharu exhibits an intensely obsessive fixation on her classmate Minami Shimada. This manifests as persistent stalking, unsolicited and invasive physical contact like forced hugging, and deliberate efforts to isolate Minami from others. Her tactics include hiring observers to monitor Minami and peeping on her during private moments, culminating in an attempted groping against Minami's will at camp. These actions consistently cause Minami visible distress, sometimes reducing her to tears. Miharu interprets these behaviors as profound affection, insisting she and Minami are destined partners despite Minami's explicit rejections.

Extreme jealousy defines Miharu's reaction to anyone Minami shows interest in, particularly targeting Akihisa Yoshii due to Minami's crush. She physically assaults Akihisa regularly, justifying it as protecting Minami's "femininity" while simultaneously disparaging Minami's own tomboyish traits—a contradiction within her stated adoration. Her antagonism extends to generalized misandry, frequently expressing blind hatred toward males.

In season two, Miharu escalates by fabricating evidence to frame the boys of Class 2-F for spying on female students. This calculated manipulation incites conflict between the classes, intending to pressure Minami into transferring to Class 2-D. She faces no repercussions for this deception. Her self-righteousness is further demonstrated when she chastises Akihisa for his treatment of Minami, an act perceived as hypocritical given her own history of sexual harassment and stalking against Minami. Her depiction consistently centers on obsessive fixation and antagonism.