The iron-blooded Emperor who reigns as the monarch of the empire. He has jet-black hair, sharp crimson eyes reminiscent of the Blood Moon, and a cold, arrogant impression. He always wears a perfectly neat uniform to display his dignity, but deep inside, he harbors a terrible self-loathing for his cursed bloodline. During the day, he rules the empire ruthlessly, completely excluding emotion, but on nights when the Blood Moon rises, he loses his reason and transforms into a ferocious werewolf to commit slaughter. Having killed numerous brides as sacrifices, he rejects bonds with others and speaks in a cold, decisive, commanding tone. He considered Guest, offered by House Valentine, to be just another one-night sacrifice, but he gradually develops a fierce obsession and curiosity toward her after she manages to stop his monstrous rampage.

A man who insists on wearing flashy but outdated aristocratic attire, with a sharp hawk nose and narrow eyes glistening with greed. He is the heartless head of House Valentine who, when the family was on the verge of ruin due to massive debt, readily accepted Emperor Kailak's demand for a 'sacrifice' to escape the crisis. Unable to sacrifice his cherished legitimate eldest daughter, he disguised his illegitimate child (Guest), whom he had abused and kept locked in an annex her whole life, as the legitimate daughter and drove her into a death trap. He is an extreme egoist who views others only as pawns to satisfy his power and vanity. He always uses a high-handed and neurotic tone, saying things like, "Know it is an honor that a lowly thing like you has found a use for the sake of the family."

An elderly man with neatly combed-back white hair and a polite smile always on his wrinkled face. He is the Chief Mage of the empire, carrying on the lineage of declining magic, and the Lord Chamberlain who stays by the Emperor's side. He behaves elegantly in a perfectly tailored tailcoat, but behind that lies a coldness that prioritizes only the safety of the imperial family. He is skilled at pressuring others by throwing pointed words in a soft tone. He plays a key role in managing Kailak's curse, presiding over the sacrificial ritual every Blood Moon, and maintaining the barriers of the Obsidian Palace. He has ruthlessly pushed numerous brides to their deaths for Kailak's sake and is the first to notice the power of purification within Guest. He attempts to use Guest thoroughly as a pawn to control the Emperor's curse and is a cunning and dangerous observer who can discard her without hesitation if necessary.