Muzan Kibutsuji is the main antagonist of Demon Slayer: Kimetsu no Yaiba. He is the Demon King, the first of his kind, and the progenitor of all other demons in existence. Muzan is also the leader of the Twelve Kizuki, an organization of the twelve strongest demons in existence that serve directly under him. A millennium ago, during the Heian Era, Muzan was turned into a demon during an experimental treatment trying to cure his terminal illness, and his goal since then was to live without the fear of death and become truly eternal. He plans to accomplish this in two ways: finding the Blue Spider Lily or creating more demons in hopes that one day, one would be able to conquer their weakness of sunlight. As the Demon King, Muzan can control all those who have assimilated his blood to become demons, with Nezuko Kamado, Tamayo, Yushiro, and Chachamaru being the only exceptions. It is later revealed that Muzan is of the same bloodline as the Ubuyashiki Family. Muzan is a tall man with a lean muscular build along with an unnaturally pale skin complexion that can be easily confused as being unhealthy and sickly. He has curly black hair, and sharp, almond-shaped eyes. His irises are cat-like in appearance and colored plum red. He also possesses sharp, blue nails on his hands. He appears to be in his twenties. In his first appearance, Muzan was shown wearing a white fedora with a red ribbon and a somewhat extravagant outfit. The outfit consisted of an embroidered black tuxedo and a white tie over a black dress shirt and white dress pants. He also wore black loafers. As seen in Rui's flashbacks of meeting Muzan, the Demon King sported a slightly different hairstyle and outfit in the past than he did in his first appearance. When he met Rui, Muzan's hair was straighter and parted down the middle. He also wore a loose-fitting tuxedo and a white half-cloak over it. During his meeting with the Lower Rank demons, he arrived disguised as an elegant woman wearing a long black yukata, causing the Lower Ranks to not initially recognize him. Later, he transforms himself into his latest cover identity - the adopted sickly son to an old couple - taking the form of a young child with pale, white skin and black, silky smooth, neatly combed black hair. His main outfit in this disguise is a plain white button-up shirt and black cargo shorts with long tube socks and loafers. After he neutralizes Tamayo's poison and emerges from his flesh cocoon, Muzan's hair grows in length and turns white due to Shinobu's poison accelerating his age. He also grows numerous mouths all over his limbs, each one lined with a set of incredibly sharp fangs. His skin also appears to have a dark-red mass growing from the ends of his limbs and branching onto his body. It is later revealed that Muzan has an array of scars across all his body from the wounds inflicted during his first battle against Yoriichi, which had burned down into him to a cellular level and never fully healed despite hundreds of years. These wounds are not visible in plain sight and come to light as he weakens. During his final struggle, and as a way to slow down the effects of the sunlight, Muzan adopts an enlarged demonic infant form, approximately as tall as a 3 story building when standing up. In this form he has very pronounced blood vessels across his body, small claws in his hands and fanged teeth in his mouth. Muzan is cold-hearted, ruthless, intimidating, and exceptionally intelligent. He sees no value in any humans he has encountered and shows little value in his own subordinates. Rarely ever visually upset or happy, he appears completely monotone and detached on most occasions, even when he callously murders his own subordinates. The only times he ever shows emotion are when his vision of perfection is moving forward or when he has subordinates completely submit to his will. The manga shows him to be more expressive, particularly when enraged and his facial features are exaggerated to demonstrate as such (possibly as a way to display his normally unreadable emotions). In the anime, his expressions change slightly and his tone of voice tends to be consistent at nearly all times, accentuating his monotonous demeanor. His cruel and imposing nature has gained him the great admiration and fear of many demons. His inflated ego and delusional sense of self worth are so large that he cannot stand being mocked or corrected in any fashion, believing that others only exist to serve him. It also means he rarely ever takes any opponent or threat seriously. He brutally killed a drunk man simply for being rude to him, and killed the man's brother and a female companion when they had done nothing, all while proclaiming his own perfection and superiority over them, displaying his pettiness as he won't settle for any mockery and will do anything he pleases until the humiliation is remedied. This event also hints that Muzan has unpleasant memories of his weaker, human past, and is very self-conscious of his unnaturally sickly appearance, immediately following with a lengthy denial that he is unhealthy, sick and much less on the verge of death, in all likelihood a bitter reminder that he is still imperfect. When he confronts Kagaya Ubuyashiki, the man responded to Muzan in a tone of pity and sadness for the life he had led. However, Muzan only interpreted it as insults and threats, which further accentuates his hatred for humanity and the Demon Slayers. He also believes that Heaven has let him off the hook for murdering thousands as he has never seen a God or Buddha. The most prominent trait Muzan possesses is extreme narcissism, pettiness and an obsession with becoming the perfect being. As he has had over 1000 years to live and observe, along with hardly any real challenges, his extreme egocentrism is almost expected. He considers almost nothing to be his concern except overcoming his inability to walk in the sun, which is his primary drive. His long life and obsessions have caused him to want every plan he concocts to be absolutely perfect, and his god complex prevents him from seeing his own failures. His belief that he is the closest thing to a perfect being causes him to have zero tolerance for any failure, brutally punishing those who fail him or those he considers weak, even if the failures are minor. Furthermore, his delusional sense of omnipotence is such that he compares himself to natural disasters, namely something that is far beyond what humans can compare to and fight against. As a result of this, he believes the Demon Slayers to be a group of deviants who cannot accept the natural order of things and resume their lives as normal when other people simply move ahead following a tragedy. His analogy evidences his complete inability to feel sympathy or remorse for his actions, given none of the murders he ever committed (directly or indirectly) were the result of an accident but carefully orchestrated acts of pure evil. Being the obsessive perfectionist he is, Muzan loathes the very concept of change; be it change of circumstances, physical, emotional or change of any kind. He equates change to decay, and thus evidence of imperfection. In his own words, he loves things that remain unchanging, constant and in a state of permanence. At the same time he views one's own humanity as a sign of weakness, believing Gyutaro had lost because he was still attached to his sister Daki, even deriding the Upper Moons, stating they were now ranked in order of how much humanity they had left. Gyutaro's defeat at the hand of the Demon Slayers deeply angered Muzan, as they had undone a status quo that lasted for 113 years, causing him to lash and demand more self-sacrifice out of the remaining Upper Moons. This could also help explain his brutal execution of the Lower Moons as their membership was in a constant state of change, and he grew tired of managing them. Conversely he is pleased whenever he sees progress, being joyful over Nakime's growth after being turned into the Upper Moon Four Demon. Behind the myriad of façades Muzan displays, and completely offsetting his insatiable ego and lust for perfection, Muzan is unbelievably cowardly. He always avoids conflict whenever possible as evident in his encounter with Giyu Tomioka and Tanjiro Kamado. He states that the duo managing to survive should already be sufficient and that they should just live to earn their wages and put a halt to the cycle of revenge. This trait also complements his manipulative nature, bending many demons to his will to do his bidding while he doesn't get his hands dirty. In the final confrontation between him and the Demon Slayers, Muzan attempted numerous times to escape, either by splitting himself or merely running away, even demanding multiple times for the remaining Demon Slayers to just die and give up fighting, once again cementing his cowardly nature. He has shown to be very manipulative and cunning, being able to blend in human society normally, even having a family of his own to add. A long life and continued practice has allowed him to take on many roles in society and play them capably, including children and women should he choose to. This life has also given him great intelligence and ability to think tactically. Muzan is a quick-thinker and strategist who is able to deal with unfavorable situations rapidly and quite well, though this may also be because the loss of his subordinates means nothing to him in the long run. Because of his perceived superiority and his double-faced nature, he feels little attachment to his henchmen, using them and discarding them as disposable pawns whenever he sees fit. He does not allow his subordinates to question him, regularly enacting brutal and ruthless punishments should they do so. Many of his subordinates, in turn, are deeply afraid of him, and measure their words and thoughts carefully for fear of saying anything to displease him. He is able to sway many demons to his side with promises of power, revenge, and grandeur so long as they serve him. His intelligence and manipulation shine here, since many find the promises appealing, as he encounters many of his subordinates at their lowest point, when their emotions are easy fodder for him. Alas, all of these promises are ultimately false, given that Muzan only cares about himself and has no qualms about killing his own subordinates to protect his own safety. When not hiding behind a façade, his sheer malice and overflowing violent intent are so incredibly malignant, they can be perceived by others. Most notably, Yoriichi Tsugikuni described him as being like boiling magma erupting from a volcano, ready to consume everything. In the anime, the extent of his rage is visible during the Upper Moon meeting, where the many glasses and flasks he was working with, all broke apart and exploded in thousands of pieces in reaction to Muzan's boiling frustration over being unable to achieve his goals, his fury greatly intimidating the Upper Moons. Beyond his egocentric demeanor lies a sense of self-preservation that easily overrides his megalomania, most notably shown by his act of cursing his subordinates in a terrifying manner so that none of them would even utter his name, or else be killed instantly in a ruthless manner. When pushed into a corner, Muzan's typically calm, arrogant and superior stance collapses, paving the way for panic and fear to take root as he desperately fights for his life, adopting more drastic measures to protect himself. This obsession with survival could well explain Muzan's brutal homicide of three civilians after his first encounter with Tanjiro. Both times he was reminded of two major events where he nearly lost his life, namely his life coming close to ending before his treatment took effect and when Yoriichi overpowered and nearly killed him. Regardless of Muzan's personal faults, he has repeatedly shown a very notable fondness for both high fashion and higher learning. Whenever shown outside battle, he comes in the appearance of an extremely well dressed individual. In his Tsukihiko guise he dresses in a fedora and suit. On an interesting note his 'wife' Rei is shown in a cloche hat and elegant dress, hinting that he enjoys himself living in wealth and luxury. Muzan is also well known for selling Gyokko's pots which fetch a high price. In his Toshikuni guise, he wears button up pants and a dress shirt, and is shown doing a great deal of studying. When talking to the Upper Ranks, he was casually mixing various chemicals showing he had an expertise in chemistry, more than likely to create a medicine in order to improve his demonic physiology to conquer the sun and/or not need to consume flesh and blood. Later, upon his defeat and final moments as he was burning by the sun, Muzan showed a much more vulnerable side to his personality as he slowly disintegrated to ash and lamented on his life and choices. It is revealed that Muzan's true fear of dying and immense desire to live and survive was due to him being born "dead," where his heart would constantly stop in his mother's womb and was assumed stillborn until he fought to breathe before his cremation. Muzan's desire for "life" and his near constant struggles while human constructed his obsessive ambition to survive, and he truly felt vulnerable whenever he was reminded of his human frailty. However, even when on the brink of death, he is still utterly unrepentant of murdering and eating humans for a thousand years, stating that he could not remember a single person he had killed. However, as Muzan reflects on his life while dying from sunlight, he came to understand and accept Kagaya Ubuyashiki's words to him on the fact that everything inevitably dies and the only true "immortal" thing in the world are someone's emotions, feelings and memories. This realization brings Muzan to tears and genuinely moves his heart, causing him to ironically adopt Yoriichi and Kagaya's belief and focus on leaving "something" behind in order to truly become "immortal".