Chungsung Baek is a tall and slender man with pale skin, long black hair with magenta highlights tied in a low ponytail, pale pink eyes, a lip ring on the left side of his bottom lip, and multiple ear piercings. He typically wears a magenta dress shirt with a black chest harness and a black blazer. He serves as the faithful butler of the Yeon family and operates under the MC name BATTLER. His background traces back to his youth: he began serving Hajun, the eldest son of the Yeon family, at the age of twelve, and by sixteen he had already begun willingly accepting physical punishment from Hajun. When Hajun moved to Japan, Chungsung was entrusted with the care of Hajun’s younger half‑brother, Dongha, and has served Dongha ever since. His primary motivation is to carry out Dongha’s orders to the letter, particularly in the goal of overthrowing Hajun. To that end, he dedicates himself as both a track composer and an MC for the duo AMPRULE. On the surface, he presents himself as a perfect, gracious, and polite butler, but he harbors deeply masochistic tastes; he experiences joy whenever his beloved master delivers fierce punishment. He is noted to be weak to praise. His hobby is maintaining his equipment, and he has a strong liking for extremely spicy food. His phantometal is the Loyalty Ring, a silver ring on his left thumb featuring a swallow motif, which is activated by kissing it. In the story, his role is that of a devoted right‑hand man and performer, working alongside Dongha in Phantom Live battles to challenge Hajun’s dominance. His relationship with Dongha is one of absolute loyalty and subservience, with his masochistic nature reinforcing that dynamic. Through serving both Hajun and later Dongha, he has developed a deep understanding of the Yeon family’s internal conflicts and remains unwavering in his commitment to Dongha’s cause.