Kaede Sajō holds the position of Vice President on Kōetsu High School's Student Council. She is the older sister of the series' main character, Wataru Sajō. Kaede has a fair complexion, chestnut brown hair partially pinned on her left bangs, and striking blue eyes (sometimes noted as purple in original material). Her school uniform features a dark-blue blazer with a blue-and-white collar over a black buttoned cardigan, white shirt, and lime-green necktie, paired with a blue miniskirt, black socks, and brown loafers. She often modifies it with cuffed sleeves and an unbuttoned collar revealing a necklace. At home, she typically wears a midriff-baring sky-blue tank top with navy edges and black gym shorts with white edges.

Kaede exhibits non-traditional, occasionally delinquent tendencies, preferring physical conflict resolution when necessary. Despite this assertive, sometimes carefree exterior, she possesses a deeply protective instinct toward her younger brother, Wataru, extending to improving the school environment for him. She maintains a relaxed attitude toward modesty in private at home, often wearing minimal clothing without concern—a behavior noted since elementary school—which causes her self-consciousness when acknowledged.

Her background includes a delinquent period that reportedly caused difficulties for Disciplinary Committee President Rin Shinomiya. Kaede's current role as Vice President reflects dedication to fostering a positive school environment, partly motivated by concern for Wataru. She actively attempts to recruit Wataru into the Student Council or Disciplinary Committee, recognizing his competence. Their sibling dynamic involves Wataru often submitting to her requests for household chores or school tasks, while Kaede demonstrates underlying thoughtfulness in their interactions.

Kaede maintains a significant relationship with her best friend, Rin Shinomiya, who is familiar with her past delinquent behavior. Her given name "Kaede" means "maple" in Japanese, and her surname "Sajō" combines the kanji for "help/aid" (佐, sa) and "castle" (城, jō), conveying meanings related to support and fortification.