Kotonoha Katsura, eldest daughter of the affluent Manami and Mr. Katsura and older sister to Kokoro, experienced a socially restricted upbringing due to her family's wealth. This isolation intensified through bullying from peers like Otome Katou and Nanami Kanroji, who envied her beauty and developed physique. Her solitude continued into high school until she encountered Makoto Itou and Sekai Saionji. Physically, Kotonoha has pale skin, maroon or violet eyes, and straight black hair extending past her waist. Her mature figure features a notably large bust, second only to her mother's in the series. While typically modest in school uniforms, her attire varies across media, including a red summer dress in *Summer Days* or a cyan bikini. Her appearance consistently attracts unwanted male attention and provokes jealousy. Personality-wise, Kotonoha presents as intelligent, gentle, reserved, and refined. She harbors androphobia, experiencing intense discomfort around men and resisting physical contact, initially straining her relationship with Makoto. Despite this, she develops extreme devotion to him, becoming emotionally dependent. When betrayed or abandoned, her mental state deteriorates into delusions, depression, or violent "yandere" episodes marked by emotionless eyes. She employs manipulation, blackmail, and murder to retain Makoto or eliminate rivals like Sekai, forgiving his infidelity while targeting others. Paradoxically, she enjoys horror films despite her otherwise prudish demeanor. Her character arc evolves significantly across media. In *School Days*, she transitions from a shy bookworm to Makoto's girlfriend, with her psychological trajectory varying by player choice: she may remain devoted, become sexually assertive, or descend into homicidal madness. The anime depicts her rape by Taisuke Sawanaga during a breakdown, followed by delusions and culminating in Sekai's murder and Makoto's decapitation after reconciliation. Manga adaptations show her accidentally injuring Makoto while attacking Sekai, only to be later killed by her. Spin-offs feature varied roles: *Summer Days* and *Shiny Days* present her as a romance option alongside her mother and sister, including possible harem outcomes. *Cross Days* portrays her paranoid over Makoto's fidelity, falsely accusing Yuuki Ashikaga and exhibiting yandere traits in specific endings. The *Valentine Days* OVA highlights her hosting friends at a hot spring and preparing occult-themed chocolate for Makoto, utilizing her family's resources for gifts. During this event, she pursues Makoto alongside Sekai and Otome, force-feeding him chocolate on the school rooftop. Her relationships include unwavering loyalty to Makoto, rivalry-turned-hatred toward Sekai for facilitating then sabotaging their relationship, and antagonism with bullies like Otome. She shares a supportive yet occasionally competitive dynamic with sister Kokoro, collaborating on chocolate-making in *Valentine Days*. Her hobbies encompass frequent library reading, martial arts proficiency in iaido enabling lethal violence, and traditional arts like piano and calligraphy, though she struggles with household chores outside specialized lemonade preparation. A *Higurashi no Naku Koro ni Mei* crossover transports her to 1983 Hinamizawa, where a supernatural "black card" amplifies her obsessive tendencies, driving Rena and Mion to attack Keiichi. After the card's destruction, she retains memories of these actions while questioning if her dark impulses will resurface in her original world.