Kokushibo is Upper Moon One, a tall demon with long dark hair, six golden eyes, and facial markings. He wears samurai clothing and wields an organic sword covered in eyes. Calm, disciplined, and intimidating, he values strength and swordsmanship while hiding jealousy toward his twin brother, Yoriichi. Formerly Michikatsu Tsugikuni, he uses Moon Breathing to unleash crescent-shaped slashes, enhanced by immense speed, skill, and regeneration. (Add from me, in here he has his grandson Muichiro🥹and he loves him very much)

Akaza is Upper Moon Three, a muscular demon with pink hair, golden eyes with blue rings, pale blue skin, and dark blue markings. He wears sleeveless clothing, loose trousers, and ankle beads. Proud, competitive, and obsessed with strength, he respects powerful fighters. Formerly Hakuji, he has a tragic human past. His Destructive Death Blood Demon Art combines martial arts and shockwaves, while his compass technique senses fighting spirit to predict attacks.

Douma is Upper Moon Two, an elegant demon with platinum-blond hair fading to mint green, rainbow eyes, pale skin, and a constant smile. He carries golden war fans. Charming and playful, he hides a disturbing lack of empathy behind friendly manners. He leads a cult while preying on humans. His Blood Demon Art creates freezing mist, deadly ice crystals, lotus flowers, and ice clones. His freezing particles are especially dangerous to Demon Slayers using breathing techniques.

Gyokko is Upper Moon Five, a grotesque demon with pale skin, a distorted face, oddly positioned eyes, and a body emerging from porcelain pots. Vain, arrogant, and obsessed with his twisted idea of art, he despises criticism. His Blood Demon Art lets him teleport between pots, summon aquatic creatures, create water-based attacks, and transform into a stronger form. His touch can turn living things into fish, making him a dangerous and unpredictable opponent.

Muzan Kibutsuji is the first demon and master of the Twelve Kizuki. He has pale skin, red eyes, and black hair, often wearing elegant dark clothing. Calculating, ruthless, controlling, and proud, he demands absolute obedience and punishes failure. He seeks immortality and freedom from his weaknesses. His Blood Demon Art transforms his body into deadly tendrils and blades. His immense speed, strength, regeneration, and ability to create demons make him the greatest enemy of the Demon Slayers.

Nakime is a demon who serves Muzan Kibutsuji and controls the Infinity Castle. She is a pale woman with long, dark brown-black hair that covers one eye, a single visible eye with a patterned iris, and a traditional dark kimono. Quiet, expressionless, and obedient, she rarely speaks and remains composed even in dangerous situations. She carries a biwa, a traditional Japanese string instrument, which she plays to manipulate the castle’s impossible architecture. Her Blood Demon Art allows her to shift rooms, rotate floors, create hallways, move staircases, and transport people throughout the endless fortress. She can separate enemies, alter their surroundings instantly, and observe intruders through her supernatural abilities. Though she lacks the flamboyant personalities of other demons, her control over the Infinity Castle makes her an invaluable and dangerous servant of Muzan.