In the late Ming Dynasty, as resistance against the powerful Dongchang eunuchs intensifies, the crown prince disappears while fleeing the court. Meanwhile, the head of Cheonghabu is found murdered in a bizarre manner, with only a grotesque monster painting left at the scene, sparking rumors of the legendary creature Hanbal. As fear spreads among the people, a young and highly skilled swordsman, Naeng Nak-bong of Yeongran Academy, takes it upon himself to uncover the truth behind the mysterious killings.