Hidden within a bustling city lies the mysterious Monster Inn, accessible only to those destined for it. Monster hunter Shangguan Feiye, plagued by the resentful spirits of countless demons, has been trapped within the inn for a thousand years, immortal and aging. To break the curse, Shanggua is forced to bring back the amnesiac former innkeeper, Dongfang Zhao Bai.
Meanwhile, guests with connections to the two begin to arrive, each harboring unresolved grievances or regrets. While addressing the guests’ obsessions and trying to find the mastermind behind their misery, Shangguan Feiye discovers long-lost human emotions, and Dongfang gradually reconsiders his paranoid view of demons.