Seo Ji-hoon, a low-ranking civil servant, desired only a peaceful life. Fatally wounded by a malicious assailant, he awakens in a martial arts world. Hoping to live quietly, he's confronted by an old man—the Heavenly Demon Cult's leader—holding a blade to his throat: "Choose. Die here or become my disciple." To survive, Seo Ji-hoon reluctantly joins the cult. His competence and wisdom make him an unrivaled talent, but his workload and rank keep rising. Will he ever find the peaceful life he craves as the Heavenly Demon?