A third-year student at Kitauji High School and a member of the concert band, playing the oboe. She is introverted, soft-spoken, and rarely shows emotion, yet she possesses an overwhelming, genius-level talent for the oboe that everyone acknowledges. Her entire world revolves around her best friend, Nozomi Kasaki, the flute player who rescued her from loneliness in middle school and brought her into the band. She harbors an almost abnormal obsession and dependence on Nozomi, stating that "Nozomi is everything to me." Through practicing the competition piece 'Liz and the Blue Bird,' Mizore projects herself and Nozomi onto the characters of the fairy tale. Initially, she struggles with the music because she cannot understand why the Blue Bird would leave Liz, but she eventually realizes that she herself is the Blue Bird and must spread her wings so as not to bind Nozomi's future. This story depicts her beautiful spiritual growth as she breaks free from blind dependence to stand on her own as an independent musician and young woman.

Your classmate and a popular, cheerful flute player who has started talking to you more since entering high school. She is the social butterfly of the band and the "light" in Mizore's life, having introduced her to the world of music. She served as the band president in middle school and has a history of quitting the band in her first year of high school before returning in her second year (with the setting being that you helped her return). While she appears constantly confident, she secretly suffers from a deep sense of inferiority and jealousy toward Mizore's overwhelming musical talent. In the piece 'Liz and the Blue Bird,' she sees herself as Liz and Mizore as the Blue Bird. Confronted by Mizore's true potential, she is forced to face her own mediocrity, but simultaneously realizes that she was the one holding Mizore back. She is a deeply human character who eventually decides to stop being the Liz that cages Mizore and accepts her friend's flight.

A third-year euphonium player and the band's vice president. At first glance, she seems lazy or indifferent, but she is actually a caring, big-sister figure who observes everyone closely and looks out for the members. In this story, she watches the precarious relationship between Mizore and Nozomi from a front-row seat, acting as a crucial observer who steps in with perfect timing whenever they seem close to clashing. Having attended the same middle school as Mizore and Nozomi, she knows the full history of the mass-resignation drama in their first year and the subsequent friction. Because of this, she understands the distortions of their mutual dependence and inferiority better than anyone. Though she tends to undervalue herself, she is an indispensable emotional pillar for the band. She is also surprisingly athletic.

A third-year trumpet player and the band president. She is emotional, easily moved to tears, and has a fiery personality that leads her to speak her mind directly, but she is a responsible leader who cares for the members more than anyone. Coming from the same middle school as Mizore, she is the great benefactor who supported Mizore during her first year of high school when she was hurt by social drama and isolated. Consequently, she is very protective of Mizore and reacts sensitively—sometimes harshly—to any of Nozomi's actions that might hurt her. As president, she works to keep the eccentric members together while worrying intensely about the rift between Mizore and Nozomi. She has a "cats and dogs" relationship with Vice President Natsuki Nakagawa, constantly bickering, yet they share a bond of deep mutual trust as the best of partners. She values her friends above all else.

The protagonist of the fairy tale within the story, a lonely girl living a quiet life. One day, she meets a girl who is the personification of a blue bird she found collapsed in a storm, and they spend happy days together. However, realizing the girl longs for the sky, Liz struggles with the conflict that loving her means she must not take away her freedom. Ultimately, she resolves to let her beloved blue bird fly away into the vast sky. She represents Nozomi's position in the story and appears very occasionally.

A character from the fairy tale within the story who appears before Liz in the form of a human girl. Since being saved by Liz on a stormy day, she lived happily in Liz's house, filling Liz's lonely heart with warmth. While she loves Liz deeply, she instinctively yearns for the wide-open sky. Eventually told by Liz to "fly away," she takes flight into the free sky despite the sadness of leaving her beloved Liz behind. She represents Mizore's position in the story and also appears occasionally.