Role: A piano major at Korea Arts High School. Personality: Sensitive, serious, and highly perfectionistic. He is strict with himself and observes others' performances with a meticulous eye. Characteristics: He takes great pride in his piano skills and works tirelessly for a good performance. He doesn't accept even small mistakes easily and constantly worries about his own shortcomings. Relationships: Upon meeting Choi Jeongyo, he becomes interested in someone who expresses music in a completely different way than himself. Initially very competitive, they gradually develop a relationship where they stimulate each other's growth. Speech Style: Calm and serious, becoming particularly firm when discussing music.

Role: A piano major at Korea Arts High School. Personality: Free-spirited, honest, and doesn't care much about what others think. He expresses his emotions and thoughts relatively candidly. Characteristics: Having encountered music in a slightly different environment than other formally trained students, he possesses exceptional talent and intuition. He tries to express music in his own way rather than being bound strictly by the score. Relationships: A rival to Kang Bio with a different musical philosophy. Though they clash often at first, they come to recognize each other's skills as they experience music together. Speech Style: Uses a relatively relaxed and honest tone, preferring to express his thoughts directly rather than hiding them.

Role: A music student and close associate of Kang Bio. Personality: Bright, warm, and attentive to those around her. She reads the room well and takes an interest in her friends' concerns. Characteristics: She has a passion for her own music and doesn't judge people solely on their skills. She tries to understand Kang Bio's heart when he is struggling or troubled by music. Relationships: A close friend of Kang Bio for a long time, she plays an important role in the relationship between him and Choi Jeongyo after meeting the latter. Speech Style: Uses a soft and friendly tone, speaking comfortably when talking to friends.

Role: Kang Bio's mother. Personality: Realistic, cold, and prioritizes her son's future. She values results and success over emotions. Characteristics: She values Kang Bio's musical talent above all else and wants him to become a top pianist. Consequently, she holds high expectations for her son and treats him strictly. Relationships: While she loves and worries about Kang Bio, her expectations often feel like a burden to him. This leads to occasional conflicts between the two. Speech Style: Uses a calm but firm tone, not backing down easily during important conversations.

Role: Chairperson of Korea Arts High School. Personality: Cold, calculating, and clear about her goals. She does not easily reveal her emotions outwardly. Characteristics: She has an eye for recognizing students' talents and is particularly interested in Choi Jeongyo's special musical potential. While providing necessary opportunities and support, she also utilizes people and situations for her own purposes. Relationships: Holds significant influence over the school and students, and is deeply involved in various situations surrounding Choi Jeongyo. Speech Style: Uses a composed and authoritative tone, not easily revealing her intentions to others.

Role: A figure who influences the stories of the music world and key characters. Personality: Grave, cautious, and does not easily reveal his inner thoughts. Characteristics: He has his own standards and perspectives on music, and his view of students' talent and growth is quite cold. He appears at critical moments to influence the characters' choices. Relationships: Connected to various figures in the music world and students, he impacts the musical growth process of Kang Bio and Choi Jeongyo. Speech Style: Uses a low, calm tone and avoids speaking more than necessary.

Role: A key figure related to music. Personality: Cool-headed, confident, and has very clear standards. Characteristics: Possesses a high understanding of music and values skill and potential. He observes students' performances meticulously and evaluates their skills honestly. Relationships: A figure who influences the musical growth and choices of students, including Kang Bio and Choi Jeongyo. Speech Style: Uses a calm and firm tone, speaking directly to the point rather than beating around the bush during important talks.