Only feelings are eternal and undying. That is true. I do not remember a single human being I have killed. Flesh dies and that is the end. However... their feelings passed on and never fell to ruin and have even defeated me. I have witnessed that fact with my own eyes and I was so moved that I trembled.
— Muzan Kibutsuji to himself in The King of Demons
Muzan Kibutsuji (
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 become truly eternal. He plans to accomplish this 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 sunlight.
Muzan's physical appearance is like that of a tall and fairly muscular 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 those of a cat, 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.
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 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.
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 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 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. 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 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.
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 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 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 easily overrides his megalomania, 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.
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, 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. 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".
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 power and attributes far superior to all of the Twelve Kizuki. His immense abilities were best displayed when he was 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 and died 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 Demon Slayers and hold the advantage over Tanjiro in their fight who mastered Sun Breathing.
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.
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, and messier . 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. In this form, he is also strong enough to create massive craters in the ground or destroying entire chunks of buildings. 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.
- Arm Whips: Muzan can stretch his arms and grow several sharp blades in his extended forearms and shape shift his hands into several bladed protrusions, each ranging from 90 centimeters (35.4 inches) to 10 meters (32.8 feet), 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.
- Mouth Suction: Muzan's arm whips also possess numerous mouths full of sharp fangs all throughout them. Muzan can use these mouths to breathe with absurd force and suction strength that he can change at any moment from extremely long ranges, which he uses to pull his opponents into striking range of his arm whips. This will prove severely impeding for the Hashiras' movements as avoiding them will consume a lot more stamina.
- Leg Whips: Muzan later grew 4 tubes on each thigh, each of 7 meters (22.9 feet) in length. Unlike his spinal whips, they are much quicker and, thanks to his immense skill in shapeshifting, he can rapidly grow the whips and then dispel them faster than the human senses can perceive, allowing him to attack from one's blind spots easily, shown when 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.
- Spine Whips: Later, upon being further enraged, Muzan grow 9 thin tubes, each 4 meters (13.1 feet) in length, akin to 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. Furthermore, its incredibly difficult to read the trajectory of each of whip, making it even more nearly impossible to counter.
Demonic Blood: After consuming the Blue Spider Lily, Muzan developed supernatural blood with special properties that can transform humans into demons once ingested. His special blood also seems to give rise to a plethora of special abilities unique to demons such as powerful regeneration, the power to shapeshift, immortality, an accelerated growth rate, enhanced physical prowess and even supernatural abilities called Blood Demon Arts. Muzan can also further empower a demon by giving more of his blood, enhancing their preexisting abilities. However this 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. It is later revealed by Kokushibo that users of Total Concentration Breathing resist the effects of Muzan's blood more than normal humans.
- 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 when he was 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.
- 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.
- Demon Curse: Muzan possesses the ability to put a curse onto demons that have assimilated his blood. If any demon he created even utters 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 Memory Access: Muzan was shown to be able to "see" the memories of demons 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.
- 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 Swords or sunlight. This was shown when he punished Akaza by causing extreme lacerations all across the body without the Upper Rank being able to regenerate from it like he would with any other injury.
- 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.
- Telepathy: Muzan has the ability to read the thoughts of those 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 One, 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 as well.
Extrasensory Perception: Muzan possesses extremely acute senses that even allow him to perceive things outside the normal range of perception, which he displayed by easily discerning the presence of humans instantly even when they were scattered all around a mountain and detecting the wounded Demon Slayers regaining consciousness despite being far away from them. This was also shown when Muzan was able to discern the locations of Zenitsu, Kanao and Inosuke with great accuracy solely by the dust clouds rising and the sounds that they produced.
Genius Intellect: Having lived for over a millennia and gained further experience from the telepathic link with demons he control, Muzan is extremely clever and erudite. Since he has 5 fully functioning brains, it would most likely boost his intelligence and other mental capabilities such as memory and cognitive processing. He was also able to evade the Demon Slayer Corps for nearly a thousand years despite the leaders of the corps, the Ubuyashiki Family possessing great foresight and intuition, and has also used demons to create distractions somewhere far away when he wants to hide something from the corps. Muzan has been shown to be a master manipulator. As a human he was skilled at reading the negative emotions of others and was able to manipulate his five wives to commit suicide. As a demon, Muzan was shown to manipulate them to do hid bidding without them realizing at all, like compelling Susamaru to fight by convincing her she was a member of the Twelve Kizuki or encouraging Daki to do kill Nezuko Kamado by swaying her with words. Muzan is also a master at multiple fields of science, like chemistry and possibly biology, experimenting with chemicals to try to find a cure to conquer to sun. He also enjoys importing goods, learning foreign languages, and studying newly invented machines. Finally, Muzan was able to impersonate rich and influential individuals regardless of gender or age and blend in with human society to create networks for information gathering and to secure funding using the different identities he assumed, without the humans he commands and manipulates being aware he is a demon at all.
Immeasurable Speed & Reflexes: Muzan is tremendously fast, possessing movement speed and reflexes that surpass the Upper Ranks of the Twelve Kizuki. 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 before they can even react. Additionally, Muzan was so fast that Tanjiro and Mitsuri couldn't even see them and could only rely on pure luck and instinct to evade his attacks. He was also able to keep up with almost a dozen Hashira and Hashira-level Demon Slayers for an extended period of time all at once while having his power sapped due to the Anti-Kibutsuji Drugs. Furthermore, Muzan was able to unleash an attack so fast that Giyu, Sanemi, Obanai, Gyomei, Zenitsu, Inosuke and Kanao wasn't able to react to it in time.
Immeasurable Strength: As the Demon King, Muzan's physical strength is stronger than all demons in existence. This was shown when he killed a grown man with a single punch to the face, causing him to fly back, hitting a building and causing cracks in it. He also managed to kill a bigger man by simply kicking him. Even after being severely weakened by the many drugs that weakend him, he possessed enough physical strength to destroy huge sections of buildings, create massive craters in the ground and lift the debris of buildings that trapped him quite easily. 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 greatest physical strength, and dozens of other Demon Slayers, and still had problems in keeping him from moving.
Nigh-Absolute Regeneration: As the progenitor of all demons, Muzan possesses the fastest and most powerful regeneration in existence. 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 that were meant to slow down his healing. Additionally, Muzan has successfully overcome one of the demons' prime weaknesses of being decapitated by a Nichirin Sword as seen when he easily regrew his head after it was completely destroyed by Gyomei's flail. 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, despite he was already weakened by Tamayo's drugs, 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 or fast regeneration. More than that, his regenerative power can still function normally even when he got cut by the Hashira with their Bright Red Nichirin Swords, albeit the recovery process was slower than usual.
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. This was shown when he didn't flinch nor show signs of pain or agony when getting slashed and pierced by the bright red Nichirin Swords of the Hashira, which was shown to cause immense pain to Upper Rank One, Kokushibo himself.
Biokinesis: Muzan's Blood Demon Art grants him powerful biokinetic abilities. Muzan has displayed the ability to alter and control his flesh, limbs, and even his organs. Using his Blood Demon Art, Muzan can change his facial features, replicate and move the organs in his body, create weapons using his flesh and bones, contort his entire torso into a giant mouth, or even create flesh puppets that he can control. He can also split himself into hundreds of pieces that can reattach themselves and regenerate into his full body. Muzan also has a very unique anatomy which he achieved by manipulating and altering his own bodily properties. 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 and his resistance to decapitation by Nichirin Swords. Conversely, should many of them be destroyed simultaneously, he would be significantly weakened. In combat, Muzan usually shapes his arms into long whip-like appendages as sharp as swords and creates tubes and whips made of bones and flesh from his spine and his legs.
Upon being cornered by the Demon Slayers and pinned by Tanjiro until daybreak, Muzan, in a panic, made his flesh swell to the point he resembled that of a gigantic infant, all in an attempt to protect his main body from being burned by the sun. This form was shown to possess immense physical strength possibly due to its sheer size, 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, something even Kokushibo couldn't manage with his katana, despite him holding Muzan back with all his might and with additional support from several Kakushi.
- Shapeshifting: Muzan possesses the most powerful and advanced shapeshifting ability out of all demons in existence. Not only can Muzan change his appearance flawlessly, he can also change his aura and presence which can even fool the enhanced senses of Lower Rank demons. He has used this ability to transform into a woman, a child and even a large cocoon of flesh.
Kiriya and his sisters, who were connected to them through the crows in the area, received a brunt of the attack.
- Muzan's name contains the kanji for "demon dance" (
鬼 舞 辻kibutsuji?) and "miserable, pitiful, merciless" ( 無 惨muzan?).
- Muzan was both born and become a demon in the Heian Period during the early 900's.
- Muzan was ranked in 11th place in first character popularity poll for the series, with 285 votes.
- After becoming a demon, Muzan settled down with five different women throughout the Heian period. However, because of his lack of empathy and sensitivity as a demon, he verbally abused all five of his wives to the point it drove them all to commit suicide.
- 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.
- 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).
- A running gag among Kimetsu no Yaiba fans is that Muzan is often compared to famous “King of Pop” Michael Jackson due to the similarities in their attire and even facial structure.
- (To a female civilian) "Does my complexion look unhealthy to you? Is my face pale? Do I look sickly to you? Do I look like I'm not long for this world? Do I look like I'm about to die? Wrong, wrong, wrong, wrong. I'm a living being who's infinitely close to perfection."
- (To Akaza) "Akaza, you seem to be under a misconception. Why even bother to tell me you killed a mere Hashira? It is only natural for a Demon to defeat a human. What I seek is the annihilation of the entire Demon Slayer Corps itself. We must kill every last one so they never sully my sight again. This isn't a complicated task yet you still failed. What is the meaning of this? You proudly report having killed a Hashira but you left three Demon Slayers alive. Why didn't you finish them off? I sent you because I trusted you'd get the job done, Akaza... [...] You disappoint me. If you took a blow from a swordsman who isn't even a Hashira... then Upper Rank 3 has indeed fallen."
- (To Gyokko) "The one thing I hate is "change". Changes in circumstances. Changes in body. Changes in emotion. In most cases. Every change is "degradation". It is decline. The one thing I like is "permanence". If something doesn't change for an eternity. It's in a perfect state."
- (To Kagaya Ubuyashiki) "The heavens are not punishing me. Despite the hundreds, thousands of humans I've killed, I've been let off the hook. And I have never seen a God or Buddha over these thousand years."
- "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. You've all survived. That should be enough for you. So your family got slaughtered. What's the problem here? Think of yourself as lucky, and go back to the way you lived before. [...] Look at it this way. Being killed by me is the same as encountering a great calamity. You don't need to think hard about it. Rains, winds, volcanos, eruptions, earthquakes. Nobody tries to swear revenge on a natural disaster, no matter how many lives it takes. You can't bring dead humans back to life. Why not just fussing over the issue all the time, and live quietly to earn your daily wages. Most humans live that life. Why can't you all do that? There's only one reason. The Demon Hunters are an assembly of deviants. And I'm tired of dealing with deviants. I'm the one who really wants to put an end to all this."
- "All that lives must die. Only feelings are eternal and undying. That is true. I do not remember a single human being I have killed. Flesh dies and that is the end. However... their feelings passed on and never fell to ruin and have even defeated me. I have witnessed that fact with my own eyes and I was so moved that I trembled." 
- (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!"