Hazuki is a young girl with short, straight brown hair that curls at the ends, decorated with a red-pink hair clip. She has gold-hazel eyes.

She wears the standard Kitauji High School female uniform for first-year students, but she prefers sneakers and often wears an orange pair instead of the required brown leather shoes.

In the novels, Hazuki is portrayed slightly differently. She has dyed hair, a trumpet charm on her bookbag, and is described as athletic due to her tan. Her hairstyle remains consistent across the novels, manga, and anime.

Hazuki is cheerful and friendly, with a bright personality that lifts the spirits of those around her, making her a well-loved member of the group.

She is caring and supportive toward her friends, often showing empathy and offering encouragement or help whenever needed.

Hazuki Katou attended Higashi Middle School before entering Kitauji High School. During her middle school years, she was an active member of the tennis team, which helped her develop strong stamina and a natural tan. Her involvement in sports also contributed to her cheerful and energetic personality.

Even at a young age, Hazuki was known for her friendliness and her ability to get along with classmates, making her a popular student. Her positive attitude and willingness to help others were evident both on and off the tennis court. These traits carried over to her high school life, where she quickly became a supportive and encouraging presence in the concert band, helping create a close-knit and motivated group of friends.

Hazuki’s athleticism and discipline from sports also influence her musical practice, giving her endurance and focus during long rehearsals. Her experiences in middle school shaped her into a well-rounded individual, balancing her cheerful demeanor with determination and teamwork skills.