Muzan's face as he looked back to find Tanjiro behind him.

Kibutsuji Muzan is the one who sets all events of Demon Slayer in motion. As the progenitor of most demons, he is the reason for the Demon Slayer Corps. He also killed the Kamado family and turned Nezuko into a demon.

Here are eight of the most interesting facts about the main antagonist Muzan Kibutsuji you probably did not know.

1. How Old is Muzan Kibutsuji

The exact number was never disclosed, but Muzan Kibutsuji is over a thousand years old. It was revealed by Urokodaki Sakonji in Chapter 11 and Episode 6. Moreover, in Chapter 127 of the manga, it was mentioned that he was in his teens and turned into a demon during the Heian period.

Urokodaki Sakonji, explaining to Tanjiro Kamado who Muzan is.

Take note that the events of Demon Slayer occurred during the Taisho era (July 1912 – December 1926). Muzan was turned into a demon during the Heian period (794 AD – 1185). At most, Muzan Kibutsuji could be 1132 years old! That is, if he was born at the start of Heian period and dies at the very end of the Taisho era.

By the last battle, his body would age by close to ten thousand years. The poison created by Insect Pillar Shinobu Kocho and Tamayo is a hybrid drug with two effects on his body. First is that the medicine will attempt to turn him back into a human. Should it fail, the second component will age Muzan by fifty years per minute.

In terms of appearance, Muzan might look like a man somewhere between his late teens up his late twenties. However, it is important to consider that he turned into a demon before he turned twenty. Speaking of Muzan’s appearance, it brings to the next question:

2. How Many Forms Does Muzan Have?

In the anime, we have seen his usual form of being a slim pale man and his female form. In the manga, however, there are other forms Muzan has taken. All in all, here are the different forms Muzan takes throughout the Demon Slayer series:


This is Muzan’s most common appearance – a man in his twenties with pale skin. He retains his wavy black hair, cut short in this form. Muzan also has his red, cat-like eyes. He wears a white fedora hat, an embroidered black tuxedo with a black shirt and a white tie underneath. As an obviously rich young man, he also wears white pants and black shoes. His outfit matches the newly-spreading Western fashion common for rich Japanese men during the Taisho era.

Muzan’s face as he looked back to find Tanjiro behind him.

In this form, he assumes the alias “Tsukihiko” and has a family. His wife, Rei, is a woman of about the same age (twenties). She has brown eyes and hair of indeterminate length since it is kept in her hat. Together they also have a small daughter.

This is the form Muzan has when Tanjiro Kamado finds him in the middle of the city. In Episode 7 of the anime, Tanjiro picked up the same scent he smelled the day his family was killed. While Muzan did not directly confront Tanjiro, he swiftly scratched and turned an innocent man into a demon. This distracted Tanjiro, and everyone else, and allowed him to leave.

Muzan’s family when Tanjiro found them in the middle of the city.

Later in the manga, Muzan would also take this form in visiting Daki during the Entertainment District Arc. It was also his appearance during his visit to the Ubuyashiki Estate.

Unnamed Female Form

He first assumed this form after the Lower Moon 5, Rui, was defeated. Muzan called all the Lower Moon demons in the Infinity Castle. During this meeting, he killed all the remaining Lower Moons, with the exception of Enmu, Lower Moon One.

In his female form, Muzan has the same looks as his Tsukihiko form, but obviously more feminine. He has redder lips, a slightly more rounded face, and her hair is obviously longer though it is tied at the back. He wears a black kimono with floral patterns. His hair is also tied in a round bun tied with gold pearl-like adornments ending in red tassels at both sides. Her fangs are also more prominent in this form.

Muzan’s female form as she appeared in the front of the Lower Moon demons.

His disguise was such that the Lower Moons did not realize that they were speaking to the progenitor himself. Aside from his appearance, the demons noted that he also changed his aura. Although, in the Episode 26 of the anime, he speaks with a similar voice to Tsukihiko, but more monotonous.


This is his young boy form. Toshikuni appears as a young boy adopted by a wealthy family. He is always seen reading. Since he went to a wealthy family, he wears a white collared shirt, black shorts, socks and shoes. He has short hair brushed towards one side. According to his foster mother, “Toshikuni” can’t get exposed to the sunlight because of a skin allergy.

Muzan under his Toshikuni disguise shortly after Kyojuro Rengoku died.

At first, his eyes appear normal. But when Akaza comes to report, his sharp demon eyes appear. Later on, after the defeat of Upper Moons Four and Five, Hantengu and Gyokko, he would again appear as a child. As Hantengu dies, he sees that Nezuko has developed a resistance to the sun.

Muzan (Toshikuni) surprised with Hantengu’s discovery. He would later kill his foster mother and the maid after this.

Upon knowing about the final piece towards his total immortality, he reverted to his more mature, Tsukihiko, form. No longer needing any disguises, he killed both his foster mother and the maid attending to them.

Final Demon Form

After Muzan Kibutsuji assassinated Kagaya Ubuyashiki, he sustained severe damage from the pillars attacking at one. It included Tanjiro and Tamayo ganging up on him. He escaped by dragging everyone to the Infinity Castle. While everyone else is preoccupied by other demons, he rested up in a cocoon somewhere in the castle.

Members of the Demon Slayer corps finding Muzan in a cocoon.

Unfortunately, all the corps members would only serve as fodder to speed up Muzan’s recovery. He would emerge in his final form. His hair, now white, flows freely down. He also seems to wear nothing at this point, with black demon marks filling his body from the waist down. Black root-like marks also crawl all over his body. Further more, maws filled with teeth are also strewn along his arms and legs.

Muzan’s final form during the final battle. As soon as he emerged from the cocoon, he devoured every demon slayer in range.

Post-War Big Baby Form

In a last-ditch effort against Tanjiro and the Demon Slayers, Muzan has swolen into a giant demon baby form. He is as tall as the three-story buildings that surround him. Big Baby Muzan tries to escape the sunlight, which remains his only weakness.

Muzan grows into a big baby creature in an attempt to still survive.

3. The Powerful Progenitor of All Demons

As the first demon, he has the ability to turn other people into demons – including Nezuko. His blood allows normal humans to have regenerative abilities and enhanced physical abilities. Some demons even gain access to supernatural abilities called “Blood Demon Art.”

Using his blood, he can give an “upgrade” to existing demons. As a weapon, he can also inject it into their enemies to cause some sort of rapid cell growth to overwhelm and kill them.

Muzan extending his monstrous arm to punish one of the Lower Moon demons.

As the first and most powerful demon, he has complete control over all the other demons. The only exception to this rule is Tamayo, Yushiro (who was turned by Tamayo herself), and Nezuko. For the rest, Muzan has exhibited the following abilities over other demons:

  • Telepathic Link – Muzan can read the demons’ thoughts. This was displayed during his assembly of the Lower Moon Demons. He can also telepathically connect with any other Demon, such as Upper Moon One Kokushibo during the final battle. He can also see what other demons see as with Hantengu. It was through this that he knew Nezuko has developed resistance to sunlight.
  • Curses – Muzan’s blood also acts as his monitoring in all the demons he turns. In the event a demon says his name, they can be killed almost immediately. This happened with Susamaru. She unintentionally uttered his name, causing large arms to grow from inside the temari ball demon.
  • Takeover – During the final war in the Infinity Castle, Yushiro was able to take over the Nakime. As he tries to manipulate the Biwa Demon’s mind, Muzan retaliates by activating his blood inside Nakime. Yushiro was almost absorbed back but was able to escape.

4. How Many Hearts and Brains Does Muzan Kibutsuji Actually Have?

Demons are already different from other people as they can regenerate limbs that are cut off. However, Muzan Kibutsuji’s body is even more different. He has a total of seven hearts and five brains. His extra neural and circulatory organs might account for his superhuman speed, agility, strength, and reponse.

The interior of Muzan’s body, as transparently seen by Yoriichi during their fight.

In the final fight, as Tanjiro passed out from Muzan’s attack, he had a flashback. He saw Yoriichi’s encounter with the strongest demon. In his transparent world view, he saw Muzan’s abnormal body. It was also the same encounter that he almost killed Muzan. Therefore…

5. Why is Muzan Kibutsuji Afraid of the Red-Haired Swordsman and the Hanafuda Earrings?

In the anime, Muzan was visibly fazed when he saw young Tanjiro wearing the hanafuda earrings. After he sent his “family” home, he recalled his near-death experience with the Red-Haired Swordsman who wore the hanafuda earrings.

Muzan’s flashback to his near-death experience in the hands of the hanafuda wearing demon slayer

To put it shortly, the Red-Haired Swordsman is Yoriichi, the user of Breath of the Sun. Curiously, his encounter with Yoriichi is different during Tanjiro’s flashback later in the manga. In the anime, it appeared like they were roadside. In the manga, they were fighting in the woods. Muzan only managed to escape by exploding himself into pieces. During this encounter, he would lose control over Tamayo but would turn Kokushibo into a demon.

In fact, during the final battle, his body would show scars that his regenerative abilities couldn’t heal or erase. These wounds that never healed are obtained from Yoriichi’s red nichirin blade.

You can find out the secrets of the hanafuda earrings passed down from Yoriichi to Tanjiro in this article.

6. Why Did He Kill Tanjiro’s Family?

The short answer is revenge. It’s very likely that Muzan caught wind of the family that holds the hanafuda earrings. Either he’s still careful of Yoriichi’s supposed descendants being just as powerful, he decided to go and finish them. You can find the full explanation why Muzan killed Tanjiro Family here.

Tanjiro’s family, with his parents and five siblings. Nezuko is on the upper right.

It also explains why Muzan turned Nezuko into a demon. Under the assumption that they are related to the user of the Breath of the Sun, he was expecting an exceptional class of demon from her. After all, his most powerful subordinate is Yoriichi’s twin brother, Kokushibo.

7. How Did Muzan Kibutsuji Become a Demon?

Before the story ends, in Chapter 201, Muzan recalls how “the shadow of death was always clinging” onto him. His heart has stopped several times when he was still in his mother’s belly. He was pronounced dead upon birth, with no pulse or breath. However, before he was cremated, he started crying.

In his youth, he was then diagnosed that he would die before he turned twenty years old. The doctor from the Heian period gave him a prototype medicine known as the Blue Spider Lily. Since he thought his disease was worsening, he killed the doctor in rage. He would soon feel the effect of the medicine – he was stronger, but sunlight will kill him. Muzan also had a craving for human flesh.

Muzan kills the doctor who gave him the Blue Spider Lily, before realizing that the medicine works.

As a trivia, Kibutsuji Muzan is from the same clan as the Ubuyashiki. In Chapter 137, Kagaya Ubuyashiki, the leader of the Demon Slayer corps, would explain all this. He said that his family has been chasing Muzan for a thousand years.

Kagaya Ubuyashiki explaining how Muzan has cursed their clan for generations.

Muzan becoming a demon cursed his family, leading to the children dying almost immediately. Before their clan died, a priest said that they must dedicate their soul to finding and defeating the demon. It has become the Ubuyashiki clan, with their wives mostly coming from the priest’s own clan.

8. What is His Goal?

Immortality. Or as Kagaya himself put it, “You dream of eternity… You dream of being indestructible.” This explains why he has created an army of demons. Muzan hopes of finding the Blue Spider Lily and make a medicine out of it to allow him to conquer sunlight.

However, he would shift his focus once he learns that Nezuko has conquered the sun, his last remaining weakness. This is also the reason for his visit on the Ubuyashiki Estate. Kagaya and Muzan would even discuss what really is indestructible.

The leader of the demon slayers faces the progenitor of demons

Muzan would realize that Kagaya is right – that memories and feelings are inherited and can’t be destroyed. In his last attempt to survive, he tried to pass all his memories and feelings to Tanjiro. Rather than leaving Tanjiro to die, Muzan wanted Tanjiro to succeed him as an invincible being.

Bonus: Muzan’s Voice Actor Toshihiko Seki

In the Ufotable anime adaptation of Demon Slayer, a veteran voice actor has provided the voice for Muzan Kibutsuji. Toshihiko Seki is a 58-year-old actor, voice actor, singer and narrator from the city of Sendai, in Miyagi Prefecture. The legendary seiyuu has also voiced a lot of other characters, including:

  • Mousse from Ranma 1/2
  • Legato Bluesummers from Trigun
  • Umino Iruka from Naruto, Naruto: Shippuden and Boruto: Naruto Next Generations
  • Genjo Sanzo from Saiyuuki Reload and Reload: Gunlock
  • Rey Za Burrel from Mobile Suit Gundam SEED Destiny
  • Danna Toramizu from MAR
  • Senketsu from Kill la Kill
  • Kaien Shiba and Aaroniero Arruruerie from Bleach
Toshihiko Seki with most of the characters he has voiced over the years.