Akaza (猗あ窩か座ざ Akaza) is a member of the Twelve Demonic Moons, holding the position of Third Superior Moon.  When he was human, his name was Hakuji (拍はく治じ Hakuji).
As a Demon, Akaza took the form of a muscular young man with skin so fair that it appears white tinged with bright green, adorned with a pattern of thick blue lines, which resemble the criminal tattoos he had as a human. The lines on his face curved across each of his eyes from under his ears to above his temples, another blue line running from the center of his hairline to the bridge of his nose, with two more lines running around his neck, three more branching off from the bottom line toward his torso.
The center line ran directly down his chest to halfway down his belly, and the other two branched off to the sides on either side of his chest to join the other two lines, with this same three-line pattern also repeating around his waist.
On her arms, lines ran down the front of her shoulders and joined two more lines that went around her biceps, before continuing down to her wrists, under which each of her fingers could be seen to be equally dark blue with an orange nail, her toes also sharing this unusual appearance.
Akaza had short bright pink hair that fell around his head, and inwardly slanted yellow eyes with pink lashes and blue sclera that looked like cracked glass, the kanji for “Upper Rank Three” etched into their irises.
He wore little clothing, only a short, sleeveless, dark pink-purple haori cut at the waist, left open to expose his chest, which was decorated with a square pattern on the back. Underneath, he wore a pair of white baggy pants that he rolled up to his knee, with a blue rope belt to hold it at the waist. Akaza prefers to go barefoot, but wears a chain of large round beads around each of his ankles.
When he was human, as Hakuji, he had the same hair, but black rather than pink, and pale blue eyes with unusually colored pink lashes. He was also very muscular as a human, and on each of his forearms he had three black criminal tattoos.
He wore a dark blue-gray yukata.
Akaza is a strong, stubborn and impulsive demon who loves to fight, especially against strong demon killers. He despised anyone he deemed weak, but sincerely respected those who were strong in his eyes, regardless of race. Whenever he met someone he considered strong, he demanded to know their name, and would not stop until he found out; he remembered all the names he memorized as a tribute to their strength. Akaza had a deep-seated psychological need to become stronger, and did not get along with his higher-ranking comrades because he saw them as his rivals. He was particularly antagonistic towards the two Higher Ranks above him, Doma and Kokushibo, and even seemed jealous of them, lashing out at Doma and vowing to kill Kokushibo. 6] Even after being beaten and decapitated in his fight against Tanjiro Kamado and Giyu Tomioka, he was stubborn and continued to fight without even knowing why he wanted more power. As a human, Hakuji possessed the same stubborn personality with a big heart and resilience. He valued others more than his own well-being and hated himself for having a life “full of empty words and promises. Even after becoming a Demon and losing his memories of his human life, parts of Hakuji’s memories influenced Akaza’s decisions; he refused to eat women, even though he knew it would make him stronger. His hatred of weak and cowardly people comes from a corruption of his human memories, where a rival dojo poisoned the well of his dojo because he was never able to beat it. Later, after remembering his entire past and all of his regrets as a human and demon, Akaza began to openly hate himself and all of his shortcomings during his life where he was not there to save or protect everyone he loved and cared about, and later admitted that the person he really wanted to kill all along was himself.
Skills & Abilities
Demonic abilities: Overdeveloped Speed: Akaza is extremely fast. During his fight with Kyojuro, Tanjiro states that they were moving so fast that his eyes could not follow their movements. 
Overdeveloped strength: Akaza possesses enormous physical strength, as he shows when he easily breaks Giyu’s sword in half with a single side punch despite the fact that Giyu was waving his blade downwards. 3] He is able to easily destroy the head of Doma, the Second High Moon, with his arm and easily pierce Kyojuro’s stomach. With his Blood Power, he is able to cause a crater in the ground just by hitting it.
Overdeveloped Regeneration: Akaza has incredible regeneration. He is able to regenerate from wounds inflicted by Tanjiro and Rengoku and even from lost limbs inflicted by Giyu with little effort. During his fight against Giyu and Tanjiro, his regeneration has evolved even further. He is able to survive even after having his head cut off  and is then able to regenerate a new one,  a feat that only Muzan had accomplished before.
Akaza has a unique ability called Technique Deployment. 6] After deploying his technique, Akaza uses his ability to create various shockwave-like attacks. He can also track his opponents by tracing their bloodlust.
Destructive Murder (破は壊かい殺さつ Hakai satsu) is a martial art, probably adapted from the Soryu style hand-to-hand combat that Akaza mastered as a human, now enhanced with his demon abilities.
Akaza’s Mental abilities
Tactical Intellect: Akaza is a genius among geniuses when it comes to unarmed and hand-to-hand combat, especially those related to martial arts. He also showed natural talent and ability in martial arts, including being able to defeat talented swordsmen and fighters from nearby dojos while learning the Soryū style from Keizo. Even as a child, Akaza could fight based on pure instinct and tactical intuition and win. This ability even surprised Giyu Tomioka, who said that Akaza could instantly evolve and adapt to any attack or technique he used, to the point where he could predict when his opponents would strike and how to counter them with equal power.
Akaza’s Supernatural abilities
Immense regeneration: Akaza has one of the most incredible regeneration abilities in the series. He is able to regenerate from wounds inflicted by Tanjiro and Rengoku and even from lost limbs inflicted by Giyu without much effort. During his fight against Giyu and Tanjiro, his regeneration has evolved further. He is able to survive even after having his head cut off and is then able to regenerate a new one, a feat that only Muzan had accomplished before.
Enhanced Senses: Like all high ranking demons, Akaza has sensory abilities beyond those of humans. He demonstrated this on several occasions when he was able to sense the caliber of his opponents, as he did with Kyojuro Rengoku, simply by looking at them. His senses were so sharp that even Giyu Tomioka recognized him .
Extrasensory Perception: This is a special extension of Akaza’s senses, obtained through years of honing his fighting instincts and supernatural abilities acquired while he was a demon. His ESP ability comes in the form of his Deployment of Techniques: Destructive Death – Compass Needle. This ability allows Akaza to gain information about his surroundings and opponents, even if they are far away from him, while giving him an accurate idea of their physical weaknesses.
Blood Demon Art
Shockwave Generation: Akaza’s Blood Demon Art gives him the ability to generate shockwaves from the pressure created by the superhuman strength of his fists and legs when he strikes. The shockwaves have the appearance of the same shade of blue as his tattoos and can be triggered from near or far. The power of the shockwaves can range from throwing opponents to creating craters in the ground. This ability, combined with his superhuman strength, makes him a formidable opponent in close or distant combat.
Indomitable Will: Akaza has an unshakable will and spirit. Although he was decapitated by Tanjiro’s Nichirin Blade, he refused to disintegrate and die, instead forcing his headless body to continue fighting. He pushed his regeneration to the point where he could regrow his head, simply because he refused to let himself be lost. Even before he became a demon, he was constantly taking hits from opponents much larger than himself and receiving countless blows, all because he wanted to heal his sick father.
Akaza’s Fighting style
Master of Unarmed Combat: Akaza’s most remarkable ability, both as a human and as a demon, is his supernatural ability in unarmed combat. Even before transforming into a demon, Akaza demonstrated prodigious skills in various forms of close-range combat, being able to intuitively create his own fighting style that proved capable of annihilating several grown men by the age of 11. 18] By the age of 18, he was able to annihilate 67 adult kendo masters with his fists alone. Furthermore, when combined with his Blood Demon Art, it makes each of his blows and strikes incredibly deadly, making him unmatched in hand-to-hand combat and martial arts skills.
Soryū Style (素流そりゅう式しき Soryū Shiki?): A bare-knuckle martial arts style taught to him by Keizo when he was living with him and taking care of Koyuki. He used it to kill 67 kendo masters with ease and it was the main inspiration for his Destructive Death style used when he became Akaza.
Bell Crusher (鈴すず割わり Suzu Wari?): A technique presumably created or inspired by the Soryū Style where Akaza strikes a sword to the side as it comes down to break it with ease.
Akaza has a unique ability called Technique Development (術じゅつ式しき展てん開かい Jutsushiki Tenkai?). Akaza begins by initiating a unique posture in the Soryū style. Currently, there are 2 versions of this posture. The first is performed by bending his knees into a semi-crouched position, extending his right arm with a half-closed fist facing his body, and bending his left arm with an open palm; the second version is almost identical, except that he opens his palm on his right arm while fully clenching his fists in a downward bend on his left arm.
- Akaza’s pseudonym contains the respective kanji for “lush growth” (猗 a?), “cave” (窩 ka?), and “sit, cushion” (座 za?).
- His name as a human contains the kanji for the archaic part of Korea (狛) and “in peace” (治 ji?).
- Akaza was the only demon of the Twelve Kizuki who refused to eat or kill women, and he had special permission to do so.
- Akaza was one of Muzan’s favorites because he was loyal and serious .
- Akaza’s technique deployment ability takes the shape of a snowflake, perhaps because of the influence of his fiancée (Koyuki’s name contains the kanji of “snow”, and she wears three snowflake-shaped hairpins).
- Many of Akaza’s attacks and techniques are named after fireworks, referring to the promise he made to Koyuki to see fireworks.
- Akaza is the only member of the deceased top brass to have met the people he knew in life when he disappeared. There are two members of the Twelve Kizuki who have been shown having this experience, the other being Rui.
- Akaza is the fourth demon who was able to overcome Muzan’s influence on himself by agreeing to stop regenerating and die, the other three being Tamayo, Nezuko Kamado and Kokushibo.
- Akaza’s Japanese voice actor has the role of Gaara in Naruto: Shippūden.
- Akaza is ranked 17th in the second popularity poll with 1982 votes.
- Akaza’s English voice actor has the role of Mahito from Jujutsu_Kaisen.
- (To Kyojuro Rengoku) “Let me tell you why you can’t enter the realm of the greatest. Because you are a human. Because you will grow old. Because you will die. Become a demon, Kyojuro. Do that, and you can train for a hundred, two hundred years. You can get stronger.”
- “There has never been a flame among all the Hashira I have killed so far. And no one has ever accepted my offer, either. Why do you think this is the case? As a fellow martial artist, I don’t understand. Not when only the chosen ones can become Demons!… To witness the hideous decline of a person with extraordinary powers… it hurts me! I can’t stand it! Die, Kyojuro… while you are still young and strong.”
- (To Kyojuro Rengoku) “Even if you fight to the death, you can’t win, Kyojuro. Those impressive cuts you gave me… are already completely healed. But what about you? A broken left eye, broken ribs and damaged internal organs… everything is beyond repair. If you were a demon, you would heal in a heartbeat. These would only be scratches for a demon. You can struggle all you want, but a human can never beat a demon.”
- (To Giyu Tomioka) “Elegant! This is a developed sword technique! Wonderful! Say your name! What is your name?! I want to remember it!”
- (To Tanjiro Kamado) “Nice moves. You trained so hard in a short time. Let me congratulate you. But man, Kyojuro did an amazing job. You were nothing but a weakling lying on the floor that night. But my God! Look at you now! Your growth is making my eyes pop out of my head. I feel pure happiness. My heart leaps. I am glad that Kyojuro died that night. He probably wouldn’t have been able to become stronger than when I saw him. And he had a foolish view of the world while remaining human.”
- (To Tanjiro Kamado) “You misunderstand something, Tanjiro. The only people I hate are the weak. I only spit in the face of the weak. Yes. I am disgusted by the weak. They make me vomit. The laws of nature want them to be eliminated.” 
- (To himself regarding Tanjiro Kamado) “I instinctively understood that I could not accept this person. He gives me an unpleasant sensation that wears on my nerves, as if fingernails were scratching metal. The dissonance makes me throw up. I misunderstand something. At first I thought I was unhappy because he was weak. But it seems that this unhappiness doesn’t go away, even as it gets stronger. It seems that everything, from his eyes and voice and words, scrapes my insides with a rasp.”
- (To himself) “On the battlefield, you have to face all unexpected situations, even if it’s the first time you encounter them, and find a way to deal with them. I can do that. Or I should be. But in the short time of this fight, I was able to get past my speed after I figured something out. Centuries of the best martial arts, only to be beaten in a direct confrontation. These eyes have no hatred or anger in them. There is no intent to kill or fight. What is captured in his eyes is most likely the “Supreme” territory I have always wanted. This must be the state of Anatta. I have always felt that this state existed, but I should have gotten there by now.”
- (To himself) “It can’t end here. I’m going to get stronger. I have to get stronger than everyone else. Stronger. Stronger still!”
- (To himself) “How could you make peace with living like poor people? Dad? This world can go fuck itself. All of you can go fuck yourselves. Why are we living like shit? Why did my father have to die? He wasn’t a problem for me. Why did he have to apologize? My father never did anything wrong. It didn’t hurt to get this punishment for stealing. They can whip me and break my bones, but I can endure anything for you, Dad. Even if it takes hundreds of years …] My father’s condition was slowly worsening. The battered bones in his back were getting weaker. I wanted to feed you more. You were definitely getting better. Why did you hang yourself? I would die for you, Dad. For you!” 
- (To Koyuki) “I will definitely heal you. Help you. Protect you. My life was worthless, it was only filled with empty promises.”