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.
While it is not explained in the anime why he did so, Muzan is shown to be living a normal life as a human. Not only that, he's married a woman and has a child with her.
For those who have watched only the first season of the anime, they will be surprised to know that Muzan turns into a woman in the second season. He keeps transforming in order to hide his true identity, and he's even known to change into an 11-year-old child to hide from Demon slayers.
Here Muzan is seen in his true, demonic form.
if i'm not mistaken, the reason why muzan shape-shift is to hide his real identity or his face from the demon slayers. I think this is also the reason why the pillars were shocked when oyakata-sama revealed that tanjiro had a brief encounter with muzan.
Abilities. Demon Body: Unique from other demons, he possesses seven hearts, and five brains. These are responsible for his powerful vitality, should any of them be harmed, he will be severely weakened.
As mentioned, a lady and a child made an appearance with Muzan in episode 8. They were his human wife and daughter. The two were never seen again after that episode.
Haruka Shiraishi: Muzan's Daughter.
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.
Since Muzan favored Gyutaro so much, he chose to incorporate the latter's sister Daki as well. The demon king believed that she was the only tool that could be used to control Gyutaro.
Muzan himself never thought highly of Daki and didn't reciprocate her devotion whatsoever, only ever talking to her to sweetly manipulate her into defeating Demon Slayers on his behalf.
14) Muzan Kibutsuji (over 1000)
Being a demon, Muzan is capable of living for many, many years. However, unlike other demons that have aged over hundreds of years. Muzan is well over 1000 years old.
The only reason why Muzan hates Doma is because of his insincerity and lack of emotions. This might sound odd, expecting emotions from a demon, but even a demon has to retain such tendencies to keep things in order.
Trivia. Anne was originally planned to be Muzan`s older sister, who died by the hand of a Demon Slayer but that idea was scrapped, as the author knew practically nothing about Muzan`s early life. Instead, Anne became his wife, by which he had two children.
Yoriichi was powerful enough to defeat Muzan; however, he couldn't do so. That's because he couldn't come down to kill his twin brother, leading to his own demise. Even to this day, Muzan is scared of Yoriichi.
3 Muzan Mainly Liked Daki Because Of Her Potential To Earn Money.
Tanjiro's ancestor was a good friend of Yoriichi and arguably was one of his only true friends. Therefore Yoriichi gave the earrings as a gift, and since then they have been passed down the generations until they reached Tanjiro.
Does Muzan have a favorite demon? Despite the fact that Muzan. is always shown to have disdain for his creations, Muzan does in fact have a favorite. On that list is Naki, made due to a convenient blood demon.
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.
Conversation. Fun fact: The reason why Enmu was able to say Muzan's name out loud without dying is because they're married!
Origin. The first demon that is said to have existed was Muzan Kibutsuji. The one who turned him into a demon was a generous doctor from the Heian Period, who wanted to save Muzan from death since, at the time, he was diagnosed with a disease which would kill him before he turned twenty.
Despite being the unstoppable force of nature in Demon Slayer, Muzan is still incapable of conquering the Sun.
Kibutsuji Muzan, Demon Slayer's King of Demons, has few weaknesses, but he still must hide from the sun. For the centuries he has been alive, Muzan's goal is to concur death and live eternally.
Since he didn't know anything about the Blue Spider Lily medicine, he needed others to find the plant for him by happenstance. This is the general reason why Muzan turned Nezuko into a demon. More specifically though, was the fact that Nezuko was of Kamado blood.