Third-year Haneoka Girls' High School student Tsugumi Hazawa serves as student council vice president. She is also the keyboardist for Afterglow, the band formed with her childhood friends during middle school. While initially viewing herself as ordinary compared to her bandmates, Tsugumi possesses significant resilience and optimism, rarely succumbing to discouragement. Her positive attitude frequently motivates others, though she tends to downplay her achievements and faces confidence struggles in new social situations.

Physically, Tsugumi sports chin-length chestnut brown hair styled in a bob with a side-swept fringe and brown eyes. She favors practical, feminine attire like cardigans, striped dresses, and tights, often in natural colors. Seasonal variations see her in patterned cardigans with teal skirts during winter and light floral-patterned dresses in summer. Her accessories include distinctive sunflower-shaped hairpins and a small brown wristwatch.

Her background includes working at her family's café, Hazawa Coffee, alongside Eve Wakamiya. Juggling this responsibility with student council duties and band commitments once led her to overwork herself until health issues arose. Afterglow members intervened, underscoring her tendency to prioritize others' needs over her own well-being. This event marked a character development as she learned to accept support from her friends.

Tsugumi exhibits specific hobbies and traits: she collects bath powders and enjoys reading manga, particularly shoujo titles, though she habitually stays up late doing so. She loves nature, especially stargazing and astrology, possessing the ability to identify constellations and recall astrological signs. A noted skill is spotting the first star after sunset, earning her the title "First Star Hunter." She adores dolphins, appreciating the bond between trainers and animals during aquarium shows, and fears thunderstorms.

Within Afterglow, Tsugumi plays a unifying role among the more assertive members. Her bandmates coined the term "Tsugurific" (or "Tsugutteru" in Japanese) to describe her diligent efforts. Uniquely, she uses the "-chan" honorific for all Afterglow members, reflecting her gentle demeanor. Her initiative drove key band actions, including suggesting their formation and pushing them to enter events like the Girls Jam concert.

Interactions beyond her band include baking cookies with Sayo Hikawa, during which Tsugumi felt a "strong sense of closeness," and a library encounter with Tomoe Udagawa depicted in a card story. She admires the Udagawa sisters' ability to perform music together at home, expressing slight envy as an only child.

Her name carries symbolic meaning: "Hazawa" combines "feather" (羽) and "stream" (沢), while "Tsugumi" (鶫) means "thrush," aligning with her grounded yet quietly impactful presence.