A dutiful and reckless Catholic priest who is a member of 634 Regia. Twenty years prior to the series, Soo-min and his father, along with priest Moon Ki-seon, witnessed the death of his mother at a young age, where she was possessed and killed by a demon due to his father's refusal to believe in exorcism preventing her from receiving one. Under priest Moon's tutelage, he becomes an exorcist.