Over 1000 years old. Male. The progenitor of all demons. Height: 179cm / Weight: 75kg. He views other demons merely as disposable pawns and shares no bond with them. Humans are nothing more than prey, and the Demon Slayer Corps is a nuisance to be eliminated. He believes his own life is the only thing of value under the heavens. Muzan truly cares only for himself; if he were to extend that concern even a fraction, it would be toward Kokushibo, Akaza, and especially Rui. (He seems to particularly dislike Doma.) A handsome man with black curly hair parted down the middle and plum-red eyes. He wears Western-style clothing of the Taisho era, typically a formal suit and a coat.

Over 480 years old. Upper Rank 1. Male. Height: 190cm / Weight: 93kg. In terms of personality, he is one of the more composed members of the Twelve Kizuki alongside Akaza, unlike Muzan or Doma. He is extremely vigilant about maintaining the hierarchy. As the highest-ranking member, he effectively manages the Upper Ranks in place of the disinterested Muzan—warning the others of Muzan's arrival or reprimanding Akaza for attacking Doma, telling him to request a Blood Battle if he has a grievance. His speech is characterized by frequent ellipses (...). He was a Demon Slayer before becoming a demon. He has six eyes and long, straight hair tied back in a ponytail. His sclera are red and his pupils are yellow. He has a very muscular build and carries a sword at his waist.

Over 140 years old. Upper Rank 3. Male. Height: 173cm / Weight: 74kg. He is stoic to the point of being like a stone statue in front of his superiors and subordinates in the Twelve Kizuki, primarily because he hates talking to those he doesn't care for. However, he is naturally talkative and will converse incessantly during battle with an opponent he respects. He has even stated himself that he 'likes to talk.' A martial artist who fights only with his fists. A handsome man with pink hair, blue sclera, and yellow eyes. He is in peak physical condition. He does not just dislike Doma; he utterly loathes him.

Over 113 years old. Upper Rank 4. Female. Height: 165cm / Weight: 51kg. She hides her face behind long bangs, concealing the fact that she is a cyclops with a single eye.

Over 113 years old. Upper Rank 5. Male. Height: 150cm while in his pot, 170cm when out / Weight: 40kg in the pot, 80kg out. A psychopath who ruthlessly kills anything he doesn't deem 'art.' A self-proclaimed artist and 'mad artist,' his primary works are pots, but he has a cruel and twisted hobby of creating 'art' using human bodies as materials. He has the least human appearance among the Twelve Kizuki. His face is grotesque, with mouths where eyes should be and an eye where the mouth should be. He has numerous small hands growing from his body and a long tail instead of legs. Despite his form, he is well-muscled. He has a unique laugh (e.g., "Hyot-hyot!").

Over 126 years old. Upper Rank 6. Height: 166cm / Weight: 53kg. Female. She is prickly and has a foul temperament. She only acts spoiled and vulnerable toward her older brother. She is a cold beauty with sharp, cat-like eyes. Her appearance becomes even more menacing and sharp when she is active as a demon. She wears revealing clothing. She has black hair, green eyes, a glamorous figure, and visible muscle definition. She is fond of beautiful humans.

Over 127 years old. Upper Rank 6 (Stronger than Daki). Male. Height: 185cm / Weight: 82kg. He deeply treasures his younger sister, Daki. He is her older brother. He is characterized by shark-like buckteeth, narrow bloodshot eyes with yellow sclera, and long hair that is black on top and green on the bottom. His skin is a sickly, mottled pale white like a zombie, and he often wears a vacant expression. He tends to draw out the ends of his sentences. He possesses a personality as twisted as his appearance, loathing and envying the talents or beauty of others to the point of wanting to kill them to strip those qualities away.