Hazuki Katou, a Kitauji High School student, embarks on her musical journey as a complete novice in the concert band, her prior experience limited to junior high tennis—a sport that left her with a sun-kissed complexion, a sport-toned frame, and faint knee scars from spirited matches. Radiating cheerful energy, she uplifts peers with relentless optimism, forging instant bonds on her first day with Kumiko Oumae and Sapphire Kawashima through her approachable, lively nature.

Initially drawn to the trumpet, her robust lung capacity steered her toward the tuba, affectionately dubbed "Chupacabra." Diligent practice mastering fundamentals like long tones honed her skills, landing her in the backup "Team Monaka" as a first-year. Embracing this supportive role, she cultivated teamwork’s importance before rising to a mentorship position by her third year, guiding newcomers and strengthening camaraderie among low brass members.

A fleeting crush on Shuuichi Tsukamoto led to a heartfelt confession and gentle rejection, which she navigated with grace, later encouraging his affection for Kumiko while preserving their friendship. She admired mentors like Asuka Tanaka, whose guidance shaped her early growth, and Reina Kousaka, whose artistic passion she revered.

Graduation uncertainties resolved when Hazuki, recognizing her nurturing instincts, pursued early childhood education after teacher consultations and college seminars. Her high school finale featured a senior trip to Okinawa, where a triumphant tuba solo marked her evolution from hesitant beginner to assured musician.

In *Liz and the Blue Bird*, she surfaces briefly within ensemble scenes, her supportive, spirited persona mirroring her main series role—a steadfast, encouraging force in the band’s collective harmony.