Kaede Shiranui is an ordinary high school student whose life shifts when she encounters Shinobu, a ninja trainee attempting to steal her underwear for a training mission. This unexpected meeting sparks their friendship, persisting despite chaotic interference from Shinobu's instructor, Onsokumaru. Kaede lives a relatively conventional home life, with parents who find the ninjas' antics amusing.

She serves as the primary voice of reason and grounded perspective within the group, contrasting sharply with the eccentric behavior of Shinobu, Onsokumaru, and the male ninjas. Kaede exhibits low tolerance for absurd or disruptive conduct, particularly Onsokumaru's lecherous tendencies, frequently enforcing boundaries through physical force or sharp verbal reprimands. Her reactions often involve exasperated meta-commentary about nonsensical situations, breaking the fourth wall to question narrative logic.

Her relationship with Shinobu forms a core dynamic, ambiguously described by Shinobu as "more than a friend but less than a lover." This includes moments of intense admiration, unexpected physical affection like groping during bathing, and possessiveness suggesting occasional romantic subtext, though Kaede's responses remain more measured. She serves as Shinobu's primary connection to the ordinary world, offering stability amidst ninja chaos.

Kaede adapts to the persistent nonsense surrounding Shinobu and Onsokumaru, developing resilience to their disruptions despite her frustrations. She balances academic responsibilities with the unpredictable demands of this friendship, often facing interrupted study sessions. Her pragmatic nature positions her as an audience surrogate, reacting with relatable incredulity while demonstrating loyalty and care for Shinobu. Her role remains consistently defined as the sensible counterpoint within the core group dynamic.