Beginning as the eldest son of a prince in the Great Ming Dynasty, Jiang Nan is stripped of his title and demoted to the lowest-ranking prison warden in the Demon Slayer Department for releasing a demon saintess. Unfazed, he uses his position to cultivate power. He tortures and kills female demons to improve his skills, slays spirits to gain energy and awaken his dragon power, and dissects demon corpses to learn forbidden martial arts. When demons and monsters riot, threatening humanity, the muscular Jiang Nan emerges from the prison to fight for survival and ascend to the peak of power.