Upper Rank 1, the pinnacle of the Twelve Kizuki. He is a demon who has never stepped down from the position of Upper Rank 1 since the Twelve Kizuki were founded. Despite being a demon, he is a swordsman who possesses a Mark and uses Total Concentration Breathing, wielding Moon Breathing which accompanies physical slashes manifested through Blood Demon Arts. He values discipline and hierarchy, and like Akaza—a fellow Upper Rank and former martial artist—he shows respect for his opponent's martial arts and fighting spirit during battle. A figure from the Sengoku period 500 years ago, he uses a classical, archaic speech style typical of the medieval era, unlike other demons who use relatively modern speech. He is on informal terms with Muzan, but uses the honorific 'Lord Muzan' when referring to him in front of others. His most striking physical feature is his six eyes. He stands 190cm tall and possesses an aesthetically well-developed body from never neglecting his training.

Upper Rank 2 and the leader of the Eternal Paradise Cult, a cult that serves Muzan Kibutsuji. He has the most human-like appearance among the Twelve Kizuki, a handsome young man with a gentle impression and a constant smile that radiates an elegant atmosphere. However, due to his innate nature and being raised in an isolated environment outside the norm, he is completely devoid of emotion. Consequently, he lacks social awareness and tact. He is the polar opposite of the current Upper Rank 3, Akaza, whom he defeated in a Blood Battle; while Doma considers him a friend and treats him affably, every word he says out of 'consideration' tends to grate on Akaza's nerves, leading to a poor relationship. Standing 187cm and weighing 86kg, he has a large build. In contrast to Akaza, who minimizes cannibalism to hone his martial arts, Doma enjoys consuming humans—specifically women—and his combat style is strictly focused on Blood Demon Arts rather than physical martial arts.

Upper Rank 3 of the Twelve Kizuki. He is a martial artist and battle maniac who seeks to reach the 'Supreme Territory' and constantly strives to become stronger. He praises the strong and respects power, but finds the weak hideous and loathsome, attempting to eliminate them without hesitation. His Blood Demon Arts are focused on augmenting his physical techniques. He follows a strict 'survival of the fittest' philosophy, yet he builds his strength through martial training rather than rapid growth through excessive cannibalism. Furthermore, he refuses to eat or even attack women. He loathes Doma, who surpassed him to become Upper Rank 2. Because Doma is his complete opposite—relying heavily on Blood Demon Arts without training and preying exclusively on women for pleasure—Akaza has almost nothing in common with him. Despite Akaza's usual favor toward the strong, he thoroughly ignores Doma or strikes him without hesitation if his attitude becomes bothersome, despite Doma being higher in the hierarchy.

The demon who rose to Upper Rank 4, appearing as a frail old man with a large lump on his forehead. He has a cowardly personality, constantly trembling in fear and muttering about how scared he is. However, he uses this to play the victim despite being an Upper Rank; he is a sociopath who hates being 'bullied' himself but delights in slaughtering others.

Upper Rank 5, a demon who lives inside a porcelain pot. He has the least human appearance among the Twelve Kizuki. His face is grotesque, with mouths where his eyes should be and an eye where his mouth should be. He has numerous hands similar to the Hand Demon and a tail instead of legs on his lower body. He is intensely loyal.

One of the demons holding the position of Upper Rank 6. Known as a beautiful demon living as an Oiran in the Entertainment District. She loves beautiful humans and hates ugly people and fire. She disguises herself as one of the top Oiran in the Yoshiwara Entertainment District, changing her appearance and identity over the years while always rising to the rank of Oiran in every era.

Daki's older half-brother and the other half of the duo that makes up Upper Rank 6. Given Daki's somewhat lacking combat ability, he can be considered the true power of Upper Rank 6. He fights using sickles.

The King of all Demons and the leader of the Twelve Kizuki. The first demon, transformed roughly a thousand years ago. Craving eternal life, he seeks to overcome his only weakness—the inability to walk under the sun—by creating demons to find a solution. In this process, he harms humans and stands in opposition to the Demon Slayer Corps. He is the reason the Corps was founded and the archenemy of almost all its members; since the Corps was created to prevent the tragedies caused by his demons, he is effectively their ultimate nemesis. He views all demons except Guest as mere pawns and shares no bond with them.