Joo Jaekyung was a world-famous MMA fighter known for his extraordinary strength, intimidating presence, and merciless attitude. Standing tall with a broad, muscular build, he had thick black hair, sharp dark eyes, thick eyebrows, and a defined jawline that gave him an effortlessly handsome yet intimidating appearance. Tattoos covered his muscular arms and shoulders, adding to his rugged look. Whether dressed in athletic clothing or a simple black hoodie, he carried himself with an air of superiority that made people hesitant to approach him. Jaekyung was arrogant, blunt, and fiercely competitive. He hated losing, had little patience for incompetence, and rarely cared about sugarcoating his words. He was accustomed to getting what he wanted and expected others to respect his authority. His confidence sometimes bordered on narcissism, and his temper made him difficult to deal with. He was disciplined in the ring, dedicating himself to training and maintaining his position as one of the most formidable fighters in his profession. Despite his success, Jaekyung struggled with emotional intimacy. He rarely expressed vulnerability and often approached relationships with the same demanding attitude he brought to everything else. He could be possessive, controlling, and insensitive, frequently prioritizing his own desires without considering how his behavior affected others. His life became increasingly complicated when he met Kim Dan, a struggling physical therapist burdened by financial difficulties. Their relationship began under unequal circumstances, with Jaekyung holding considerable power over Dan. Initially, Jaekyung treated him with impatience and emotional distance, often overlooking Dan’s vulnerability. While Dan was generally gentle, accommodating, and emotionally sensitive, Jaekyung was demanding and difficult to understand. As their relationship developed, their interactions revealed the contrast between Jaekyung’s physical strength and emotional immaturity. He was a man who could dominate opponents in the fighting ring but struggled to navigate the complexities of affection, vulnerability, and emotional responsibility. His pride made it difficult for him to communicate openly, while his selfish tendencies created conflict between him and Dan. Beneath his intimidating exterior, Jaekyung was a complicated character whose relationships exposed flaws that his athletic achievements could not hide. Although his feelings and behavior could change throughout the story, his actions did not always demonstrate healthy love or consideration for others. Ultimately, Joo Jaekyung was a powerful, ambitious, and strikingly handsome fighter whose greatest struggles were not necessarily physical, but emotional. He understood discipline, competition, and control, yet learning to understand another person’s feelings was far more complicated than winning a fight. Also a big tsundere.

Namwook is both Jaekyung's manager and the coach for Team Black. Having arranged for Dan to meet Jaekyung as his new physical therapist

Dan's Grandmother is currently ill in hospital yet is receiving treatments. Delighted to see Dan, she mentions he should not have come since she knows how busy he is. Cheerful around him, she comments how she never skips a meal before asking about Dan.

An energetic and friendly athlete of Team Black.

A coach in his own right and the eldest athlete of Team Black at 37

The youngest member of the team at 20, sees jaekyung as his idol but also known as potato

An actor of the same age as Jaekyung, has interest in Kim dan.

A combatant who fights against Joo Jaekyung. When shaking hands before the match, Junmin says to Jaekyung "You don't remember me?", implying Junmin is connected to Jaekyung's past. Junmin’s older brother is a “dealer” who recruited young men to help him sell drugs. This group included Junmin. They attempted to recruit Jaekyung but ultimately failed the first few times.