Komari Koshigaya is a 13-14-year-old second-year middle school student at Asahigaoka Branch School, born September 14th. She occupies the middle position in the Koshigaya family, with an older brother named Suguru and a younger sister, Natsumi. Her mother, Yukiko, frequently treats her as a young child, fueling Komari's yearning to be perceived as more mature. Standing approximately 135 cm tall (though she sometimes claims 140 cm), Komari is notably short. She has waist-length brown hair featuring bangs that cover the left side of her face, emerald green eyes, and occasionally visible fang-like teeth. Her wardrobe often consists of childlike clothing or her school uniform, partly because her mother delays purchasing new clothes until she outgrows her current ones. Komari's personality centers on deep insecurity about her height and childish appearance, sharply contrasting with her strong wish to be seen as an adult. This insecurity causes frustration, especially when comparing herself to others like the younger but more physically developed Hotaru Ichijō. She is academically responsible but easily frightened by supernatural concepts, making her a frequent target of Natsumi's pranks. Despite this, Komari exhibits consistent kindness and loyalty, often looking out for her friends. She initially avoids asking for help to preserve a grown-up image but gradually learns that seeking assistance, such as with cooking, is acceptable. Her superstitions and fears are recurring traits, and she diligently uses sunscreen due to UV concerns. Relationships significantly shape Komari's experiences. She shares a close yet teasing dynamic with Natsumi, who exploits her fears but also relies on her sisterly support. Her friendship with Hotaru is mutual, and Komari appreciates being called "Senpai," though she envies Hotaru's maturity and physical development; unbeknownst to Komari, Hotaru harbors a crush on her. Renge Miyauchi is another close friend, though Komari dislikes Renge's nickname for her, "Koma-chan." Interactions with her family reveal underlying warmth, particularly with her mother, despite Komari fearing her anger. Throughout the series, Komari demonstrates development in practical skills. Initially poor at cooking—evidenced by burnt meals—she improves through practice and guidance, notably mastering curry and rice balls. Her emotional growth involves gradually accepting her stature and childish tendencies while recognizing that maturity involves collaboration rather than solitary efforts. The spin-off "Non Non Biyori: Remember" shows her progressing to high school, indicating further off-screen development. Additional details include her ownership of a plush bear named Shokichi-san, a tendency toward cat-like eye expressions when lying or disappointed, and a preference for sweet foods over natto.