Kato Otome is a student in class 1-4 at Sakakino Academy and a member of the girls' basketball team. She is a classmate of Kotonoha Katsura and has been a friend of the protagonist Makoto Ito since their time in middle school. Born on April 1, her physical statistics include a height of 164.1 centimeters and AB blood type.

Otome's outward personality is direct, headstrong, and authoritative among her peers. She is often described as lively, cheerful, and possessing a strong sense of personal loyalty and justice. However, this confident exterior masks a more complex internal world, particularly when it comes to romance. Despite her aggressive demeanor in social situations, she becomes noticeably timid, tender, and shy in the presence of Makoto, for whom she harbors deep feelings.

Motivation is a key driver for Otome's actions. She has secretly loved Makoto since their school days, a period spanning approximately three years by the time the story begins. This long-standing unrequited love was so powerful that it pushed her to achieve academically. She lacked the grades to enter Sakakino Academy but worked exceptionally hard to gain admission solely to attend the same high school as Makoto. Her jealousy over women who approach Makoto manifests as possessiveness, leading her to attempt to drive away any perceived rival to ensure that if she cannot have him, no one else will.

In the story's class structure, Otome serves as the de facto leader of a trio of friends consisting of Minami Obuchi, Natsumi Koizumi, and Kumi Mori. This group plays a significant role in the narrative by systematically bullying Kotonoha Katsura, the quiet and well-endowed classmate who becomes Makoto's first romantic interest. The bullying stems from Otome's jealousy and her belief that Kotonoha uses her body to seduce men, which she uses to justify her harassment. Significantly, her bullying campaign never extends to heroine Sekai Saionji. The reasons for this are practical: Sekai is in a different class and, unlike the isolated Kotonoha, has her own powerful social circle of friends, including Nanami Kanroji and Setsuna Kiyoura, who would retaliate if she were targeted.

Otome's key relationships define her role. Her primary relationship is with Makoto, whose obliviousness to her feelings is a central frustration. He is largely unaware that she leads the bullying against Kotonoha, believing her to be mostly innocent. Outside of school, her family includes a younger sister, Karen, who teases Otome by remarking that she has "no heart and no chest," pointing to a possible inferiority complex regarding her smaller bust size. Her parents also affect her worldview; her mother, Nadeshiko, has a history of threatening other women, and her father is a philanderer, which contributes to Otome's general hostility toward women she perceives as seductive.

In terms of development, Otome does not achieve a relationship with Makoto in the anime adaptation. She eventually works up the courage to confess to him, but she ultimately withdraws from the chaotic central love triangle as events spiral toward their tragic conclusion. In the original visual novel, however, players can follow her specific route to achieve a "Good Ending" known as "A Steadfast Heart Is Rewarded". In this path, after Makoto grows tired of the obsessive attention from Kotonoha and Sekai, he turns to Otome, and she finally realizes her long-held wish to be with him. Their resulting relationship is portrayed as a frequently bickering but ultimately affectionate couple.

As a notable ability, Otome is a talented athlete. She joined the basketball club specifically to be closer to Makoto and is a sports scholarship student, implying a high level of skill where she finds few worthy opponents. Despite her unsympathetic role as a bully, her deep insecurities, difficulties with honesty, and unyielding three-year pursuit of her first love present a portrait of a girl whose passionate and direct nature becomes a source of both her strength and her suffering.