Mary Kikakujo is a student at Private Aichi Symbiosis Academy and a member of the Supreme Five Swords, tasked with enforcing rules among the male students. She possesses a French-Japanese heritage, sometimes slipping into French when flustered or excited, and uses a Japanese-French dictionary to recall certain words. Her birthday is November 29.

She fights primarily with Western-style fencing using a rapier, delivering precise thrusts aimed at nerve clusters to impair opponents. Her swordsmanship merges Jigen-ryū techniques with classical fencing, allowing rapid consecutive strikes. Her signature techniques include the Flick (diverting thrusts to bypass defenses), Redoublement (unpredictable flailing attacks), Touche par Touche (downward thrust), and Touche par Dessous (upward thrust). Her combat relies on exceptional footwork and enhanced speed for effective counters.

Outwardly strict with school regulations, she presents as a proper young lady while harboring a hidden perverted streak. After her duel with transfer student Fudou Nomura, she develops romantic feelings for him, particularly because he refused opportunities to touch her breasts. This rejection altered her view of him, leading to frequent quarrels with Rin Onigawara over monitoring Nomura. She exhibits jealousy when other girls approach him and occasional disappointment when he ignores her advances.

Physically, she has long blonde hair styled in two front curls and a braid, blue eyes, and fair skin. Her standard uniform is a white collared shirt with blue cuffs, a maroon necktie, a brown rapier holster belt, a blue miniskirt, white high socks with a blue garter, and brown shoes. She has a well-endowed figure and stands approximately 161–164 cm tall.

Additional trivia notes her blood type as O and her reliance on a book to recall terms like "kiss."