Muzan

As far as his physical appearance is concerned, Muzan has the appearance of a young man whose age is around 20 years old or so; he has short hair styled in curls with some strands hanging down on his forehead. Like all Demons, Muzan has feline-like eyes, in his case, plum-red in color and his fingernails are pointed and blue in color. When he was a human, Muzan dressed in the Heian Era style using a traditional hitatare, had longer hair reaching down to the small of his back and his eyes were completely devoid of any sparkle. In his first appearance, Muzan was shown wearing a white fedora with a red ribbon and a somewhat extravagant outfit, consisting of a black embroidered tuxedo and a white tie over a black dress shirt and white dress pants. He also wore black loafers. As seen in Rui's memories of meeting Muzan, the Demon King once sported a slightly different hairstyle and outfit in the past. When he first met Rui, Muzan's hair was straighter and parted down the middle. He also wore a loose tuxedo and a white half-cape over it. Muzan has the ability to change his physical appearance to disguise himself, appearing either as a black-haired woman dressed in a kimono or a small child. His ability to disguise himself was so perfected that he could even change his presence and confuse his own subordinates. Muzan adopts a new physical appearance which consists of his skin becoming paler, his hair growing longer and taking on a grayish white tone due to the effect of the drug created by Shinobu to force the aging of his body; on his limbs he is completely covered with thick jaws with large, sharp teeth and a strange dark red mass completely covers his skin.

Muzan is callous, ruthless, and exceptionally intelligent. He sees no value in any human he has encountered and shows little value in his own subordinates. Rarely visually upset or happy, he appears completely drab and aloof on most occasions, even when callously murdering his own subordinates. The only times he shows emotion is when his vision of perfection advances or when his subordinates completely submit to his will. The most prominent trait Muzan possesses is extreme narcissism, his megalomania, and an obsession with becoming the perfect being possessing immortality. The latter behavior is derived from his own Thanatophobia having experienced close proximity to death literally since his own birth, both in his days as a human and in his later encounter and confrontation with Yorīchi Tsugikuni, the first Demon Slayer to use the Sun's Breath. An encounter that nearly ended his life and left Muzan with a strong post-traumatic stress disorder causing him to have a violent reaction when he remembers his own near-death experiences, being able to overcome this trauma once he understands, already in his final moments, the words of Kagaya Ubuyashiki where he understood that although living beings, especially humans, are destined to die, their thoughts remain in eternity which leads him to transfer his cells to Tanjiro to turn him into a Demon who can do what he could not achieve: overcome his weakness to sunlight. His egocentrism and delusional sense of self-worth are so great that he cannot stand being mocked or corrected in any way, believing that others only exist to serve him. It also means that he rarely takes any opponent or threat seriously. He brutally killed a couple of drunk men

Muzan has unpleasant memories of his weaker human past, and is acutely aware of his unnatural sickly appearance, coming on the heels of a long denial that he is not healthy, sick, let alone on the verge of death. In all likelihood, a bitter reminder that he is still imperfect. Being someone so obsessed with the idea of ​​perfection, Muzan despises the very concept of change; be it change of circumstances, physical, emotional, or change of any kind. He equates change with decay, and thus, evidence of imperfection. In his own words, he loves things that remain unchanged, constant, and in a state of permanence. Muzan's feminine form reflects his monotony. Muzan being a human, lived in terror at the thought of dying. Muzan seeing himself cornered shows his most cowardly side.

Being the first Demon, Muzan's powers surpass anything seen before. Muzan is so strong that he was able to withstand a fight with five Pillars and Tanjiro at the same time. So strong is he, that he was able to leave Tanjiro on the brink of death, as well as several Pillars, were it not for the timely intervention of Chachamaru and the antidotes he gave the Pillars and Tanjiro so they could survive the effects of the poison present in their blood. After 30 minutes of combat, Muzan manifested whips from his legs, which increased his attack speed exponentially, to a point where he instantly defeated five exhausted Pillars: Gyomei, Giyu, Sanemi and Obanai, as well as Zenitsu and Inosuke at the same time, while leaving Kanao paralyzed with fear and with her sword broken. [15] It is later revealed that Muzan was becoming increasingly slower, due to the effects of the aging medicine provided by Tamayo, which accelerated his age massively. Despite everything, he was able to subdue the pillars that faced him, as well as Tanjiro who was just learning to use Sun's Breath. [16] His strength, speed, endurance, and regeneration capabilities are superior to any conventional Demon and are even considerably superior to those of the 12 Demon Moons, adding also his exclusive amount of unique abilities that he has.

Unique Body Constitution: Unlike other demons, Muzan possesses a unique body with which he can make use of his complex abilities. His interior has five brains and seven hearts. If a simultaneous attack affects these vital organs, he will be considerably weakened. In addition to this, Muzan can move his vital organs within his body in order to avoid a fatal blow. Body Manipulation: Muzan can blow himself up at any time when his life is in danger by dividing his body into several fragments of flesh which are later regrouped to be able to escape from his enemies. He was able to divide himself into 1800 pieces of flesh of which a good part were destroyed. He used this ability to be able to escape from Yoriichi when they had their confrontation. Superhuman Strength: Muzan is extremely strong despite his fragile appearance. He can deliver very powerful blows capable of sending a human flying through the air with a kick or smashing his head against a solid wall without the slightest effort. Speed: Muzan is also fast, being able to attack an ordinary human with his claws and infect them with his blood fast enough for no one to notice. Even when one of his lower Moons wanted to escape from him, being able to get away a considerable distance, without help from Nakime, in the blink of an eye he had already decapitated him. Regeneration: Like all the Demons he creates, Muzan can regenerate from any kind of wound, even recovering his limbs when they are severed; he is also able to withstand an explosion at close range, being able to rebuild his body as quickly as it is destroyed [18], but the highest point of his regeneration is that he can even regenerate his own head when it is cut off, unlike the Demons he creates which die when decapitated, direct exposure to sunlight being the only way to kill Muzan

Demonic Blood: It is one of his main abilities; with his blood, Muzan can turn an ordinary human into a Demon who will be under his control thanks to a component present in his blood which when entering the bloodstream of a human, causes their cells to begin to transform, thus becoming a human being. The physical changes and powers acquired by the newly created Demon vary depending on the number of people he eats, and can even use a supernatural ability called Demonic Blood Techniques by manipulating his blood for various offensive or defensive purposes. However if a human receives Muzan's blood in large quantities, their cells will not withstand the physical changes and will self-destruct causing a horrific death by causing the person to literally dissolve into their own flesh. Nullification of another Demon's regenerative qualities: As Tamayo explains, Muzan, being the one who gave rise to all Demons, is the only one capable of killing others of his kind by nullifying the regenerative qualities of their blood and cells, being able to inflict mortal wounds on any Demon who dares to oppose him, destroying their body completely without exposing them to sunlight or through the use of Nichirin Weapons. Curse: When Muzan turns a human into a Demon by inserting his blood, he transmits his cells through their bloodstream, thus ensuring that he shares a bond with the Demon; in this way, he can know their location, read their mind, sense their presence and if he wishes, destroy their cells. Muzan uses the latter to destroy the demon if for any reason it dares to reveal his identity or if it tries to betray him. However, if a demon has enough willpower to resist Muzan's control, by refusing to eat human flesh or drink human blood, they can escape the curse.

Omnipresence: Muzan can see through his eyes what the demons he has created see, thus ensuring that he will not be betrayed by his creation. Extrasensory Perception: Muzan can sense the presences of humans and demons alike, and can also sense a being's bloodlust and thus know their intentions. Absorption: Muzan possesses the ability to assimilate and absorb any individual who comes into contact with his body, also gaining their qualities and powers if he absorbs a Demon. Shapeshifting: Muzan can change his physical appearance to disguise himself, appearing with a different aura and presence to confuse his enemies and allies alike. It has been seen that Muzan can take many forms, from a woman, a child and even turning into a mass of meat with fangs which he uses to tear apart his opponents. Combat form: Once Muzan leaves the flesh cocoon where he was locked, he adopts this new form in which his speed and strength are severely increased despite the weakened state in which he was left due to the drug that Tamayo tried to introduce into his body, he was able to easily eliminate an entire squadron of Demon Hunters and devour their bodies as soon as he left the flesh cocoon where he was. The mouths with sharp teeth located throughout his body once he adapts this form not only serve as his main form of offense in battle, but also have the purpose of helping him recover faster as he can use his jaws to tear apart his opponents and eat their flesh, simultaneously killing his opponents and recovering his strength at the same time