Kaoru Nonogusa is a second-year student at Kin'gyoku Academy and a member of its student council. She acts as a devoted subordinate to the council's influential leader, Shizune Mejirou, frequently aiding his schemes against rival Ōgyoku Academy. Her loyalty is driven by fervent romantic devotion to Shizune, often manifesting as visible blushes and timid behavior in his presence. Despite her feelings, Shizune remains oblivious, preoccupied with power struggles.

Initially characterized by shyness and low self-confidence, particularly outside council duties, Kaoru carries out Shizune's assignments. This includes an early mission to manipulate protagonist Kabamaru, leveraging her appearance to gain his trust, highlighting her initial reluctance to engage beyond her role. Her design emphasizes femininity, featuring long blonde hair and pink attire, contrasting with peers like Mai Ookubo.

As the series progresses, Kaoru gradually sheds some reticence, forming tentative bonds with Mai and Kabamaru. She moves from aloofness to reluctant camaraderie during collaborative events, such as espionage missions against Ōgyoku. A pivotal moment involves infiltrating Ōgyoku's dormitories with Kabamaru to gather intelligence, where they discover a love letter from Ōgyoku's leader to Mai. Though comedic, this operation reinforces her commitment to Shizune's goals despite personal reservations.

Kaoru's emotional arc centers on unrequited love. Her devotion persists through Shizune's manipulation of Kabamaru and escalation of school conflicts, including recruiting ninja-trained students for confrontations. Even as Shizune's tactics grow morally ambiguous, she remains supportive, often serving as his closest confidante. Her romantic pursuit remains unresolved by the series' end. During the climactic conflict between the schools, her involvement is passive, adhering strictly to Shizune's directives without independent action or resolution to her personal storyline.