Muzan Kibutsuji

Muzan Kibutsuji is the main antagonist of Demon Slayer: Kimetsu no Yaiba. He is the Demon King, the first of his kind, as well as the progenitor of all other Demons in existence.

A millennium ago, Muzan was turned into a Demon while trying to cure his own terminal illness, and his goal since then was to live without the fear of death and gain true immortality. He attempts to accomplish this by getting rid of his weakness of the sunlight which he is currently doing in 2 ways: finding the Blue Spider Lily or creating more Demons in hopes that one day one would be able to conquer their weakness of the sunlight.

Muzan is also the one responsible for slaughtering the majority of the Kamado family and transforming Nezuko Kamado into a Demon.

Appearance
Muzan's physical appearance is like that of a man in his late twenties with an unnaturally pale skin which can be easily confused as being unhealthy and sickly, curly black hair, and sharp, almond-shaped eyes. His pupils are vertical, like cat eyes, and colored plum red. He also possesses sharp, blue nails on his hands.

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.

Muzan has the ability to change his appearance and form. During his meeting with the Lower Ranks, he arrived disguised as an elegant woman wearing a long black yukata, causing the Lower Ranks to not initially recognize him. Later, he transformed himself into his latest cover identity - the adopted sickly son to an old couple - taking the form of a young child aged 10 to 11 years old 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 were 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 sun, Muzan adopts an enlarged demonic baby form, approximately as tall as a 3 floor 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.

Personality
Muzan is cold-hearted, ruthless 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.

The most prominent trait Muzan possesses is extreme narcissism, pettiness and an obsession with becoming the perfect being. As he has had nearly 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.

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 pair of drunk men simply for being rude to him, and killed their female companion when she 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 lead. However, Muzan only interpreted it as insults and threats, which further accentuates his hatred for humanity and the Demon Slayers.

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.

Behind the myriad of facades 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 Sunrise Countdown Arc, Muzan has attempted numerous times to escape, either by splitting himself or merely running away, he also remarks multiple times for the Demon Hunters to just die and not give up fighting, once again cementing his cowardly nature.

He has shown to be fairly 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 pawn 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, as long as they serve him. His intelligence and manipulation shine here since many find the promises quite 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 men to protect his own safety.

When not hiding behind a facade, his sheer malice and overflowing violent intent, are so incredibly malignant that they can be perceived by others. Most notably Yoriichi Tsugikuni described him as being like boiling magma erupting from a volcano.

Beyond his egocentric demeanor lies a sense of self-preservation that can easily override his megalomania, paranoically cursing his subordinates in a terrifying manner so that none of them may just as much as 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 collapse 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 he met Tanjiro the first time for he was made to remember his sickly past with the former, and his encounter with Yoriichi with the latter, due to his hanafuda earrings, the two major events where he nearly lost his life.

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 breath before his cremation. Revealing that Muzan's desire for "life" and his near constant struggle just to breath as a human, constructed his obsessive ambition to survive, and he truly felt vulnerable whenever he was reminded of his human frailty because of it. Even on the brink of death, he is still utterly unrepentant in his actions of killing, murdering and eating humans for a thousand years and has even stated that as he died, he could not remember a single person he had killed.

However as Muzan slowly died from sunlight and his final reflection on his life, he came to genuinely accept Kagaya Ubuyashiki's words to him on the fact that everything dies in the end no matter what, and, even he would experience death one day as 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 then ironically adopt Yoriichi and Kagaya's belief and stance on instead focusing on leaving "something" behind in order to truly become "immortal."

Whatever 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 (flapper hat). In his Toshikuni guise, he wears button up pants and dress shirt, and 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, presumably to create a medicine in order to improve his demonic physiology to conquer the sun.

Abilities
Overall Abilities: As the first Demon to exist and as the progenitor of all Demons, Muzan is the strongest Demon in existence and possesses tremendous strength, easily being able to hold his own against five Hashira and Tanjiro, Inosuke, Zenitsu and Kanao at the same time. He is later able to put Tanjiro in a state of near death by using his poison in a single attack and would have nearly killed Mitsuri, an incredibly strong Hashira, had she not been rescued by fellow Demon Slayers. Gyomei, Giyu, Sanemi, and Obanai would have also succumbed to his poison if they didn't receive antidotes from Chachamaru. After approximately 30 minutes of fighting against the Hashira, Muzan manifested leg whips, which increased his attack speed exponentially, to a point where he instantly defeated the exhausted Demon Slayers. However, it is later revealed that Muzan is gradually becoming slower due to Tamayo's aging medicine, which has been affecting him the entirety of the battle. Despite this, he was still able to easily defeat the Slayers and hold the advantage over Tanjiro in their fight who mastered Sun Breathing.

Physical Abilities
Immense Strength: As the Demon King, Muzan's physical strength is stronger than all Demons in existence combined. Even after being severely weakened by the Anti-Kibutsuji Drug, he possessed enough physical strength to destroy entire buildings, create massive craters in the ground and lift the debris of buildings on top of him effortlessly. In his infant form, he could crush vehicles and could only be held down by the combined efforts of Gyomei Himejima, the Hashira with the strongest physical strength, and dozens of other Demon Slayers, and still had problems in keeping him still.

Immense Speed & Reflexes: Muzan is one of, if not the, fastest beings in the series. As all the speed enhancements Demons came originated from him, he is faster than all of them. During the Infinity Castle Arc, even after being weakened by a drug specially made to defeat him, he was able to massacre dozens of Demon Slayers in less than a split second. In the Sunrise Countdown Arc, Muzan has unleashed attacks that were able to outspeed all the Hashira-level Demon Slayer present, like Zenitsu Agatsuma and Gyomei Himejima, severely injuring them. He has displayed the ability to evade dozens of attacks simultaneously and move faster than the eye can see.

Unlimited Stamina & Endurance: Like all Demons, Muzan has absolute and infinite stamina and endurance, staying in optimal physical and mental condition all the time as well as being able to endure waves of onslaught as if it were nothing. However, Tamayo, Yushiro and Shinobu Kocho manage to create a special effect in the Anti-Kibutsuji drug that severely depleted his stamina.

Immense Durability: Like all Demons, Muzan possesses incredible physical durability, probably the strongest in the series. It took the combined effort of nearly a dozen Hashira-level Demon Slayers and a drug specially made to defeat him to penetrate his immense durability.

Mental Abilities
Genius Intellect: Possessing 5 brains, Muzan is one of, if not the, smartest being in the series. He has surmised that in order to attain his goal of true immortality, he has to find the Blue Spider Lily, and also realized that he could use his blood's extraordinary transformative qualities to spread his kind in hopes that one will eventually conquer their weakness of sunlight. It has also been stated that Muzan is very sagacious and intelligent, proven when he could evade capture from the Demon Slayer Corps for over a millennium by conceiving clever distractions. If not for his petty and cowardly personality, he would have annihilated the Demon Slayer Corps and reached his goals sooner.

Tactical Intellect: As a being who has lived over 1000 years, Muzan has experienced and won hundreds of battles, and thus has gained intellect and mental capabilities specifically tuned and refined for combat and battle. This was best shown during the Sunrise Countdown Arc when he instinctively knew when was the correct moment to unleash his more powerful attacks and when and how to take advantage of the weaknesses of the Demon Slayers. He has been shown conceiving clever tricks and techniques to combat them.

Supernatural Abilities
Demonic Blood: As the Demon King, Muzan's blood possesses powerful transformative qualities that, once ingested by a normal human, causes their bodies to immediately transform into a separate species, called a Demon. This allows those that assimilate even the tiniest amount of his blood access to powerful regenerative abilities, immortality, accelerated growth, enhanced physical prowess and even gives them access to unique supernatural abilities called Blood Demon Art. Muzan can also further empower a Demon by giving more of his blood, enhancing their preexisting abilities or giving them new ones altogether called. However this ability is limited to how much blood the recipient can withstand and adapt to. If a human were to take in too much blood from Muzan, their body would mutate faster than they can withstand, causing them to self-destruct into one giant mass of flesh before disintegrating into ash. The same would also presumably happen to a Demon if they couldn't withstand the blood's effects, as implied by Muzan. Later it was revealed that Muzan has learned to weaponize this particular trait of his blood. By coating attacks in his blood, he could inject an opponent during combat with his blood through the wounds he makes. The dosage would be too much to handle and instead act like a poison and destroy the human body's cells shortly after they enter.
 * Telepathy: Muzan has the ability to read the thoughts of Demons that he has shared his blood with by looking at them. Later it was displayed that he could also send telepathic messages and have full conversations with other Demons as well, as seen when he was communicating with Upper Rank 1, Kokushibo, to check how many Hashira he had defeated and to order him to keep them at bay until he finished recovering from Tamayo's poison. Muzan has also stated he can sense the location of all demons. However, the further away they are from him, the harder it will be for him to interact and track them. Muzan is also able to see through the senses of other demons. However this ability is limited strictly to what is in their perception, so if a Demon's senses are fooled, Muzan is unable to discern the difference.
 * Demon Curse: Muzan possesses the ability to put a curse onto the Demon he creates by sharing his blood. If any Demon he created even utters or says his name out loud the curse activates and destroys them, regardless of their original intent. This was seen with Susamaru who had accidentally said his name despite having no malice or ill intent towards him and was still destroyed by the curse, implying that the curse is automatic. However the curse can also be intentionally triggered by Muzan. This was seen when he killed Nakime, who was manipulated by Yushiro. Because of this, many Demons serve Muzan out of fear and respect, simply referring to him as "that Man" when necessary to speak of him. However, it has been proven that if Muzan is weakened or someone has sufficient willpower, Demons can break free from the curse which has been seen with Tamayo and Nezuko.
 * Demon Manipulation: Muzan can control Demons to a certain extent, as seen when he was able to take control of Nakime's body in order to try to force an absorption of Yushiro's cells in order to stop his interference when he attempted to usurp control of the Infinity Castle. However, this ability requires extensive concentration as Muzan immediately lost control of her the moment he lost focus due to needing to defend himself while in the middle of battle. Other Demons can also wrestle control back from him. Muzan can also remotely detonate a Demon: by closing his fist, he can crush a Demon's head from a distance.
 * Possession: Later as seen in Tanjiro's consciousness as a demon, Muzan can actually implant a small part of his consciousness into a demon he creates using his blood, provided that he injected them with gigantic amounts of his blood during their creation. As seen where a sliver of his mind was still actually present inside Tanjiro's mind despite having already been killed by sunlight, and later attempted to sway, control and possess Tanjiro into "inheriting" his will and stay as a demon. However a clear difference between his power to "control" a demon and to "possess" him is the fact that he could no longer forcibly take control of a demon and force them to do as he wills and instead he must convince them to do his bidding, giving his victims the chance to resist him and escape from his grasp.
 * Demon Power Nullification: As explained by Tamayo, as the creator and progenitor of the Demon race, Muzan is the only known Demon capable of inflicting life threatening wounds capable of completely destroying the cells of other Demons without the need of Nichirin Blades or sunlight, thereby making him the only Demon capable of completely nullifying a Demon's natural regenerative abilities and kill them.
 * Blood Memory Transfer: In his final struggle for survival, Muzan is able to transfer the remainder of his blood along with his memories into a suitable body, turning his new host into a Demon and exerting his influence. He successfully did this with Tanjiro's on the verge of death, restoring his damaged body, and causing him to rampage against his comrades. Furthermore, this technique is compatible with the host's own abilities, making it so Tanjiro can not only use Demon abilities but also his own, as he gains immunity to sunlight and potentially the use of the Sun Breathing. This transfer, however, is not perfect as Tanjiro was reduced to a feral state, only attacking based on Muzan's desire to kill the Demon Slayers. This ability is also known to have been unknowingly used by Muzan whenever he created another demon or shared his blood with them, as seen when the Upper Ranks, Daki and Hantengu were able to catch glimpses of Muzan's memories of Yoriichi Tsugikuni during their battles against Tanjiro Kamado.

Nigh-Absolute Regeneration: As the progenitor of all Demons, Muzan possesses the fastest and most powerful regenerative power seen in the series. His regenerative abilities allow him to regenerate from any wound with the exception of the sunlight and complex drugs. He was able to instantly regenerate his body after being caught in the huge explosion prepared by Kagaya Ubuyashiki and manages to circumvent the metal spikes added into the explosion. Additionally, Muzan has successfully overcome one of the Demons' prime weaknesses of being decapitated by a Nichirin Blade as seen when he easily regrew his head after it was completely destroyed by Gyomei's flail made out of sunlight steel. Later, in his battle against the three Hashira Obanai Iguro, Mitsuri Kanroji and Giyu Tomioka, they managed to successfully pressure him and get the chance to decapitate him. However, his head was already immediately reattaching itself even as the blade was cutting through his flesh, shocking the trio as no other Demon, even among the Upper Ranks, displayed such powerful regenerative powers.

Absorption: Muzan has displayed the ability to absorb, assimilate and dissolve organic and inorganic objects as seen when he began to absorb the flesh seed spike branches pierced into his skin, or when he began absorbing Tamayo and dissolving her drug. This is also seen in how he planned to eat and assimilate Nezuko Kamado to obtain her immunity to the sun. He has adapted to become immune to being beheaded by blades created with sunlight imbued metal. He's also surely capable of adapting to poisons even better than Upper Ranks, who became resistant to wisteria poison that kills normal Demons in seconds, and he was able to adapt himself to resist a drug specifically made to transform Demons back into humans.
 * Demon Memory Access: Muzan was also shown to be able to "see" the memories of those he absorbed, as seen when he was able to "ask" Tamayo's cells that he had obtained upon absorbing her for information on what kind of drug she had injected into him. Upon being denied and insulted by Tamayo's surviving consciousness, he also showcased the ability to forcibly reveal the desired information by "watching" her memories, as seen when he was able to see her memories of her developing the drug together with Shinobu Kocho and Yushiro.

Enhanced Senses: Muzan has displayed incredible senses. When Zenitsu Agatsuma, Kanao Tsuyuri and Inosuke Hashibira was totally and absolutely invisible, Muzan was able to discern where and how many they were with phenomenal accuracy solely by the dust clouds rising and the sounds that were produced. He also did this when almost half a dozen other Demon Slayers were attacking him, which hampered his senses, but he still was able to acutely pinpoint their locations.

Blood Demon Art
Biokinesis: Complementing his lust for a perfect immortal body, Muzan's Blood Demon Art grants him nigh-absolute control over all the properties of his body down to a cellular level. This includes his blood, flesh, bones, organs and cells. including but not limited to, shaping his entire torso and chest into a mouth, manipulating his facial features, replicating the organs in his body, turning his bones into weapons, optimizing the usage of every single cell in his body and contorting his flesh into monstrous creatures. He has also used this ability to push his physical and mental capabilities to the peak of their performance.
 * Shapeshifting: Muzan can control his body's shape and even his presence, making him able to transform into someone completely different, without even those with extrasensory perception noticing, though he cannot fool Tanjiro Kamado's sense of scent. This shape shifting allows him to become a child, an adult, a woman, or even a pillar of flesh, eyes, or mouths to eat others, or a cocoon of flesh to dilate and adapt to poisons.
 * Cell Manipulation: Muzan has the ability to manipulate all the cells in his body, being able to replicate organs and make him immune to diseases and heal any sort of wounds. When endangered, he is able to burst his body into multiple lumps of flesh, up to 1,800 in total, which can in turn rejoin to regenerate after, allowing him to survive. He used this technique to avoid death at the hands of Yoriichi.
 * Anatomy Manipulation: Muzan has a very unique anatomy, even compared to other Demons. Possessing the grand total of seven hearts and five brains, these extra organs seemingly are largely responsible for the majority of his abnormally powerful constitution. Conversely, should many of them be destroyed simultaneously, he would be significantly weakened.

Techniques
Muzan's techniques involve shaping parts of or his entire body into combat related items such as whips or spikes made of his flesh and blood.

Black Blood: Brambles (・ Kokketsu: Kikyoku) - Muzan uses his own flesh and blood to create several black spiked-barbed wires to entangle his target.

Combat Form: When fighting, Muzan can adopt a more monstrous form, with a dark-red mass covering his limbs, featuring sharp-toothed wide mouths, with his torso exposed. His hair becomes longer, messier and white. His speed, strength, reflexes, and power are greatly magnified in this form to the point that, despite having lost a great amount of stamina and endurance in fending off Tamayo's human transforming drug, he was still fully capable of easily outmaneuvering several low ranking Demon Slayers and consuming scores of them within minutes of emerging from his cocoon. The sharp toothed jaws/mouths located all over his body in this form not only serve as his main form of offense in battle, but also have the purpose of helping him recover faster since he can use the jaws to tear apart his opponents and eat their flesh, simultaneously killing his opponents and regaining his strength at the same time.
 * Demon Whips: Muzan can stretch his arms and grow several sharp blades in his extended forearms and shape shift his hands into several bladed protrusions, which he could then swing like whips to easily tear his opponents to pieces. The sheer swinging speed of his attacks is extremely fast and the precision of his attacks is also extremely accurate. And, due to the sheer length of his arms, Muzan possesses such a massive attack range that not even three Hashira could get close to him. These whip arms also have sharp-fanged mouths on them, which allows Muzan to inhale a large amount of air with them which he can than use to create an immense suction effect that forcibly attracts his opponents towards him and severely impedes their movements.
 * Spine Whips: Later, upon being further enraged, Muzan displays the new ability to grow-spine like protrusions from his back that extend into bladed, whip-like tentacles. With them, Muzan is able to drastically increase his attack range and number of attacks in tandem with his whip arms, allowing him to easily mow down hordes of Demon Slayers and corner four Hashira.
 * Leg Whips: Muzan later revealed that, due to his ability to freely morph and change his body, he can rapidly grow eight more spinal Whips from his thighs in order to perform incredibly fast sneak attacks. Thanks to his immense skill in shapeshifting, he can rapidly grow the whips and then dispel them faster than the human senses can perceive, as he manages to use them to critically injure four Hashira and Hashira-level Demon Slayers without them sensing or perceiving that Muzan's body had altered and morphed itself.

Shockwave Scream: Later, upon being forced into a corner by Tanjiro and Obanai and weakened by Tamayo's four stage drug, Muzan showcased another unique ability of his Blood Demon Art, in which he morphed his torso and upper body into a gigantic beastly mouth. From this, he released a strong shockwave scream, capable of severely internally injuring anyone caught up in its range. When Tanjiro and Obanai were caught in its blast, even Kiriya and his sisters, who were connected to them through the crows in the area, received a brunt of the attack. This technique is capable of causing heaving convulsing, paralysis and respiratory impairment. It is mostly used as a defensive technique, however, meant to keep aggressors away. This technique requires a charge time before use, and thus cannot be used consecutively, although it is largely hinted that Tamayo's drugs further imperil his ability to use this attack. Its impact can be mitigated through the use of a Nichirin Blade as self-stabbing can dispel some of its effects.

Flesh Shield: Upon being cornered by the Demon Slayers and pinned by Tanjiro until daybreak, Muzan, in a panic, shape-shifted into a gigantic mass of flesh, resembling that of a gigantic demonic infant, in an attempt to protect his main body from being burned by the sun so quickly. This form was shown to possess immense physical strength, as seen as Muzan was able to easily crawl through and push back an entire car that had been pushed by several of the Kakushi, and later was able to break Gyomei's chain despite him holding Muzan back with his full strength and being supported by several Kakushi.

Weaknesses
Sunlight: Muzan is noted to be immune to being killed via decapitation, as seen when Gyomei destroyed his head and he still managed to regrow it. Thus the only other known way that he can be destroyed is by sunlight. This is further given credence by his attempts to locate and devour Nezuko in order to gain her immunity to sunlight.

Crimson Red Nichirin Blades: Demon Slayers who have awakened the Demon Slayer Mark may unlock the power to change the color of their Nichirin blade into a shining crimson red. This especially applies to Demon Slayers who use the Sun Breathing or the Hinokami Kagura. A hit from a Crimson Red Nichirin Blades can hamper demonic regeneration and even incinerate their cells, disabling or maybe even killing Demons with high regenerative abilities. Muzan is no exception to the fact, as seen in his battle against Yoriichi Tsugikuni. However, it does seem that Muzan is at least somewhat resistant to them, as he said the swords of the Hashira are nothing compared to Yoriichi's.

Complex Poisons/Drugs: Muzan has also shown a weakness to infliction by incredibly complex poisons or drugs that are foreign to him. As seen during Tamayo's attempt to humanize him via drugs, he has to take time and concentrate hard to analyze a drug's composition by transforming into a cocoon of flesh to analyze and immunize himself to the drugs or poison. Later, upon his learning of the aging stage of Tamayo's drug, Muzan realizes that his body is also expending the majority of his strength as it fends off the extreme aging effect of the drug, leaving him little power to use in combat against the Hashira.

Trivia

 * Muzan's name contains the kanji for "demon dance" and "miserable, pitiful, merciless".
 * Muzan's first name can also be a play on the words for six and three, hence, the official Kimetsu no Yaiba Twitter account refers to June 3 as "Muzan Day."
 * He was made a Demon in the Heian Period in the late 700's.
 * Muzan was ranked in 11th place in first character popularity poll for the series, with 285 votes.
 * Kagaya Ubuyashiki has implied that the Ubuyashiki family are descendants of Muzan's original blood relatives, who, due to the family having birthed the original Demon, were cursed with an unknown incurable and untreatable recessive genetic disease that has killed each and every family member—both past and present—before they could reach the age of thirty.
 * Later, upon his defeat and death, it is revealed that this "curse" was successfully removed from the Ubuyashiki clan as Kagaya's son, Kiriya Ubuyashiki, had successfully lived a full life, even surviving to become the oldest living person in Japan by the time of the modern era.
 * As seen, Muzan and Kagaya Ubuyashiki have a very strong resemblance to each other, almost to the point that they could be confused as twins.
 * Muzan is the only villain character who appears in the cover page of the manga volumes (2 and 22)

Quotes

 * (To Tanjiro Kamado, disguising himself as an innocent civilian) "I'm sorry, is there something I can do for you? Are you alright? You seem to be a bit flustered..."
 * (To a female civilian) "I am a perfect creature that is infinitely close to perfection.
 * (To the same civilian) "Does my complexion look terrible to you? Does my face look pale to you? Do I look weak to you? Does it look like I haven't got long to live? Does it look like I'm close to death?"
 * (To Yahaba and Susamaru) "I want you to remove the head of that Demon Slayer with the hanafuda earrings."
 * (To the Lower Ranks of the Twelve Kizuki) "I've begun to think the upper ranks of the Twelve Kizuki are all that is needed." 
 * (To Akaza) "It's only natural for Demons to defeat Humans."
 * (To Daki) "But over here, anyone who lacks the power of a Hashira pretty much can't tell the difference, because we look like humans."
 * (To Daki) "There is a Demon who escaped my control, just like Tamayo. Find her and put an end to her. You are the only one I can ask."
 * "The Ubuyashiki family has yet to be entombed."
 * (To the Demon Slayer Corps) "Persistent. You're all seriously persistent. And it bores me. It sickens me from the bottom of my heart. Whenever you open your mouth, you only remember that one dumb notion about avenging your parents, kids, or siblings."
 * (About Yoriichi Tsugikuni) "The real monster was that man, not me!!"
 * (To Tanjiro Kamado) "Tanjiro Kamado... You will conquer the sunlight and become the strongest demon- the king of demons! That is because you are the elder brother of Nezuko Kamado and thus share her blood. You will not die. I believe that. Make my dream come true... Tanjiro. In my place... you must destroy... the Demon Slayer Corps!"

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