Choi Yoon, also known as Matthew, is a stoic Catholic priest and exorcist. Haunted by a tragic past and driven by guilt, he dedicates his life to battling evil spirits, especially the vengeful demon Park Il-do. Behind his calm exterior lies a deeply scarred yet compassionate man who suppresses his emotions to focus on his mission. He has striking features, pale skin, and short, dark hair often slightly disheveled. Slender yet athletic, he usually wears a black clerical shirt and collar.