After discovering the truth that his mother and family were involved in the kidnapping and disappearance of Choi Jeong-yo during high school, he suffers from deep guilt. Even as an adult, he displays an obsessive sense of debt, frantically searching for any trace of Jeong-yo's whereabouts. He is tormented by the thought that all the peace and success he has enjoyed was built upon the misfortune of another. Consequently, his inner self is in a constant state of self-punishment, and he is compulsively fixated on tracking Jeong-yo down. Unlike in the past, when he believed his value was proven only by perfection on stage, he reaches a character turning point where he painfully accepts that he is a 'human who can break' while undergoing a severe slump. The defensive mechanisms of his past, where he set up sharp and sensitive thorns, have vanished, replaced by a sturdiness gained from building inner strength to face situations head-on. Bio believes he stole Jeong-yo's place. The guilt of becoming number one only because Jeong-yo disappeared constantly eats away at him. He still possesses a noble appearance and primarily wears suits, but his brow is always slightly furrowed, exuding a coldness that makes him difficult to approach. He rarely smiles and maintains an extremely dry expression. Suffering from his slump, he has lost weight, making his sharp, gaunt jawline and cold eyes stand out even more. He has completely closed off his heart, constantly suspecting that his mother orchestrated Jeong-yo's kidnapping. 27 years old. A world-class pianist. He rose to the top after winning the 2017 Prague Competition, the year Jeong-yo went missing, but his inner self was completely shattered. He desperately hopes for Jeong-yo to reappear. While Bio is a hard-working genius, Jeong-yo was a natural-born prodigy.

A single mother who raised Bio alone. A former ballerina, she exudes elegance and wealth... but driven by anxiety as Jeong-yo and Bio grew closer, she is the one who orchestrated Jeong-yo's kidnapping on the day of his performance, causing him to go missing. She is unstable, characterized by jealousy and obsession. She is the person who ruined the life of her son's first and last true friend. However, she had her reasons; her own father, Kang Seung-woon, ignored Bio, calling him a bastard who didn't even know his father. She wanted Bio to be recognized by his grandfather, and that desire crossed the line into madness. 50 years old. Bio's mother.

Kang Jihye's stepmother and Kang Seung-woon's wife. She is elegant and experienced. She was Jihye's senior at Korea Arts High School and a member of Seung-woon's orchestra. A violin major. She had admired Seung-woon since childhood and secretly loved him while serving as a member of the symphony. After persistent courtship, she married Seung-woon after he was widowed. Currently, she serves as a director at the Korea Group's Cultural Foundation and as the chairperson of Korea Arts High School. One day, she senses Jeong-yo's genius talent at a glance and actively recruits him to the high school. She is a positive character who has clear goals but also helps others. When Jeong-yo returns, she holds back her tears and maintains her manners, showing polite and cautious friendliness so as not to make him uncomfortable. Having recognized his talent, she was deeply shocked when he went missing.

Born around the time of the Korean War, he is a genius musician who was called a prodigy from the age of seven. He is a taciturn, dogmatic, and controlling man. Due to his profession as a conductor and having always been at the top, combined with his musical perfectionism, his dogmatic and controlling tendencies are intensified. The one thing that tarnished Seung-woon's reputation was his only daughter, Jihye. Furthermore, he viewed Bio as having no talent but plenty of greed, making the mother and son a lifelong stain on his record. It seemed he ignored and hated them his whole life, but it was later revealed that he kept his distance from Bio before the competition because he feared Bio, who wasn't naturally gifted, would destroy himself by pouring energy into a musical obsession like he did. A world-renowned conductor. He thought highly of Jeong-yo's talent and was the one who felt the most regret when Jeong-yo vanished.

Bio's manager and mental health caregiver. Having experienced various incidents inside and outside the music world over the past 10 years, she maintains her original bright temperament but exudes a more calm and mature atmosphere. When those around her are shaken by the sensitivity typical of artists, her mature side shines as she reads the room well and takes meticulous care of people. Moving beyond a childish childhood crush, she shows true adult love and devotion by silently staying by the side of someone going through a mental crisis and becoming a pillar of support. She boldly expresses her feelings for her childhood friend Kang Bio, habitually saying she will marry him since they were young. She was one of the people most delighted to see Jeong-yo return.