Suzu Nekoyama is a petite 16-year-old first-year high school student who moved from the countryside to the city, now living with her older sister, Tamaki, a university student. This shift made adjusting to urban life and social interactions challenging for her.

She possesses black wavy hair and sharp, slanted eyes frequently likened to a cat's. Suzu typically wears black tights and needs glasses for her slight nearsightedness during class. Her small chest size causes her self-consciousness.

Shy, reserved, and easily flustered, Suzu displays tsundere tendencies, often reacting coldly or defensively before revealing caring feelings. Although she identifies as a dog lover, her traits are distinctly feline: she enjoys fish, dislikes mice, prefers solitude or confined spaces like karaoke rooms, naps frequently during the day, exhibits stubbornness, and has a sensitive tongue intolerant of hot foods. Notably, catnip induces intoxication-like effects, prompting uncharacteristically bold or provocative behavior.

Her romantic interest focuses exclusively on Yachiyo Inugami, beginning with a fated introduction through mutual friend Aki Hiiragi. This attraction is complicated by acute jealousy when Yachiyo interacts closely with others, including Aki or Mikine Nezu, or when Suzu finds photos of unfamiliar girls among Yachiyo's belongings. This jealousy manifests as sulking, overactive imagination leading to misunderstandings about her importance to Yachiyo, and occasional physical aggression. Despite deep investment, chronic shyness and embarrassment prevent Suzu from articulating her feelings directly, especially in response to Yachiyo's overtly affectionate or perverse advances.

At school, Suzu relies on Aki for social guidance and emotional support, forming a close bond where Aki acts as her caretaker. She joins the biology club alongside Yachiyo, Mikine Nezu (a mouse-like classmate), and Yukiji Ushiwaka (a cow-like senior). Her interactions with Mikine develop into a playful yet tense "cat-and-mouse" dynamic mirroring their animal traits. She also encounters classmates like the monkey-inspired Sora Sarutobi and the bird-like Hibari Torikai.

Her development is incremental, centered on navigating her relationship with Yachiyo through cycles of jealousy, awkwardness, and mutual attraction. Small moments—accepting Yachiyo's invitations despite embarrassment, expressing concern during conflicts, or dreaming about Yachiyo while ill—signal gradual emotional investment. However, her core traits of shyness and defensive jealousy remain consistent throughout.