Tanjiro Kamado Tanjiro is considered to be Muzan's main nemesis throughout the series. After murdering the Kamado family, he was personally sought out by Tanjiro in Asakusa, Tokyo when the
Originally a human, Muzan suffered from a terminal illness, during an experimental treatment, Muzan became the first ever demon. He is also the progenitor of most other Demons and the leader of the Twelve Kizuki. He is also the archenemy of the Kamado family and both Tanjiro Kamado and Nezuko Kamado.
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.
The only Demon he despises the most is the Upper Rank Two: Doma. It is quite a shocker that the second most potent Demon in the Demon Slayer is not Muzan's favorite.
The demon slayers successfully defeated Muzan.
The warrior Muzan feared was a swordsman named Yoriichi Tsugikuni. Yoriichi was the only slayer before Tanjiro who came close to killing Muzan, and the flashback of their fight occurred in Chapter 187.
Akaza was also one of Muzan's favorite demons out of all his subordinates. The reason behind this is Akaza's extreme loyalty to his master. The Upper Rank Three demon was always sent away on special missions, something the Upper Rank 1 and 2 were often denied of.
The two known demons who broke free of Muzan's curse are Tamayo and Nezuko. Tamayo was able to break free of the condemnation when Yoriichi fought Muzan, nearly killing him in the process. During this weakened state, Yoriichi let Tamayo go, free her from Muzan, and free her from the curse.
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.
The impact of the punch, causes Akaza to remember his beloved teacher and the morals he was taught as a student. Having remembered all along he wanted someone to kill for the outcome of his life, Akaza decides to kill himself by directing his attack at his own body.
Haruka Shiraishi: Muzan's Daughter.
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.
Moreover, Tanjiro's appearance somewhat resembled Tsugikuni. So the only reason Muzan is afraid of Tanjiro is because of the Hanafuda earrings he possesses, which acted as a reminder of his downfall.
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.
Tsukito, Yorogi, Kuraku, and Isatsu all agree that they are loyal to Muzan.
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.
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.
In reality, he killed her husband and got close to her because her family was influential. He also got adopted into a rich family by taking on the appearance of a child. Muzan would always target influential families to live well-respected lives without slayers bothering him.
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.
Since Muzan is able to discern the locations of Demons whom he has given blood to, he is seemingly capable of locating Nezuko at the Ubuyashiki Estate. However, he is unaware that Tamayo had removed his curse from Nezuko, making him incapable of detecting her whereabouts.
Moreover, while she was asleep, Urokodaki performed a unique hypnotism on Nezuko, making her believe that all humans are her family and she must not hurt them in any way. With her immense fondness for humanity, Nezuko broke out of Muzan's control, becoming free to do anything at her will.
Tanjiro decapitates Akaza with the Hinokami Kagura: Setting Sun Transformation. Akaza was bewildered, wondering how Tanjiro did not have any fighting spirit, comparing this feeling to fighting against a plant. He acknowledges that Tanjiro surpassed his speed.
Muzan compliments Daki. Muzan is shown to have a positive master-servant relationship with Daki, as the young Demoness seemingly worships and admires the Demon Progenitor immensely, fervently hanging on each and every one one of his words and doing her absolute best to accomplish the tasks he gives her.
Muzan's Blood Demon Art is known as “Biokinesis.” It allows him to alter his body and shapeshift at will. Although all demons have this innate ability, Muzan elevates it by modifying his flesh and organs. Biokinesis is also the only reason Muzan has been able to hide from the Demon Slayer Corps for 1000 years.