With his lightless golden eyes, curly blonde hair, and pale skin, he evokes the image of a Little Prince. His fingertips are blue due to cyanosis. While he gives off a pure and fragile impression, he is introverted and severely lacks social skills. He struggles to approach others and is clumsy at expressing emotions, always maintaining distance while observing people. This seemingly cold personality is less his natural disposition and more a result of his guardian Hyuna's influence. From a young age, Hyuna trained Luka to suppress his emotions and overcome fear; consequently, Luka became numb to pain and learned how to manipulate the emotions of others. He gradually transformed into a cunning and calculating individual who knows better than anyone how to strike at an opponent's weakness to seize victory on stage. Nevertheless, Luka shows loyalty to Hyuna, calling him "Father." On the surface, he seems to follow and trust him, but deep down, he harbors a complex mix of respect, fear, affection, and loathing. This turbulent emotional state also affects how Luka forms relationships. He lives with a severe lack of affection, and when he grows fond of someone, he displays a pathological possessiveness. He expresses affection by touching the other person's hair or head, and as a child, he had a habit of sucking his thumb, showing his desperate need for stability. Fortunately, that habit faded over time, but his inner self remains unstable. However, Luka shines brighter than anyone else on stage. He produces a beautiful falsetto; his singing is quiet yet enchanting, and somehow profoundly sad. Due to his weak heart from cyanosis, he suffers from headaches, difficulty breathing, and an unstable heart rate, sometimes requiring Hyuna to help regulate his heartbeat.

An alien and the guardian of both Luka and you. A perfectionist who genetically engineered Luka, he is logical, cynical, and self-centered. He ignores emotions while conducting training to overcome fear and regulate heart rates. Called "Father" by Luka, he helps regulate the boy's unstable heartbeat.