Kaede Shiranui is a blonde or ochre-haired, blue-eyed high school student attending Shirazuchi High. Her life takes a chaotic turn when ninja-in-training Shinobu targets her underwear during an exam ordered by Onsokumaru, an incident disrupting Kaede's studies and causing her to fail her own exams. Despite this disruptive start, Kaede forms a deep friendship with Shinobu, becoming her primary confidante. She stands as the series' most sensible and grounded individual, frequently acting as the exasperated straight man reacting to the absurd antics of Shinobu, Onsokumaru, and the male ninjas. Kaede tolerates no harassment or nonsense, often employing physical force or sharp retorts to quell others, especially Onsokumaru's lecherous behavior.

Residing with her parents makes Kaede the sole main character depicted with a family. Her parents find the ninjas' chaotic visits amusing, while Kaede finds them irritating. Despite constant disruptions to her studies and daily life, she exhibits patience and remains protective of Shinobu, accommodating her friend's eccentricities and naivety. Their relationship is complex: Shinobu expresses intense admiration and romantic interest, describing Kaede as "more than a friend but less than a lover." Kaede's own feelings fluctuate between discomfort, protectiveness, and genuine care. This dynamic leads to Shinobu's fantasies or awkward advances, which Kaede typically deflects or endures with mixed reactions.

Kaede frequently breaks the fourth wall, commenting on events' absurdity or expressing meta-awareness about being in an anime. She participates in various episodic activities like festivals, Christmas celebrations, and mushroom hunting with Shinobu and the ninjas, often questioning their logic. Bathing scenes involving Kaede occur multiple times, including a bubble bath fantasy, a shower scene, and a hot spring episode where she bathes with Shinobu and Miyabi, typically interrupted by Onsokumaru's antics. Her role remains consistently the voice of reason amid escalating chaos, maintaining a pragmatic outlook while navigating the surreal world of ninja mishaps and Onsokumaru's schemes across all media, with no significant character evolution or background expansion beyond this established role.