Her most prominent trait is her extraordinary growth rate, possibly due to the high amount of blood she received from Muzan Kibutsuji when he turned Nezuko into a demon and the fact that she doesn't need to consume human blood to survive.
Tanjiro and Nezuko Kamado's lives were forever changed when Muzan Kibutsuji, the King of Demons, slaughtered their family and left Nezuko to become a demon.
Nezuko, the young sister of the main protagonist Tanjiro, has a special Blood Demon Art called Exploding Blood that allows her to ignite her blood into pink flames and even summon it from thin air. Unlike other demons, Nezuko doesn't consume humans to grow stronger but instead rests to unlock her full potential.
Secondly, Muzan would probably… eat Nezuko and Tanjiro in the hopes of obtaining their sun-resistance abilities, and also since he wouldn't be able to convince them to become demons to work under him. This would allow him to become the ultimate demon.
Despite this, Muzan still managed to pass on his blood and will to the deceased Tanjiro, reviving him as the new Demon King.
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.
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.
Nezuko, on the other hand, never was under Muzan's curse, it would seem. Instead, she used her will to protect her brother and other humans to fight off the curse. This is probably why Nezuko sleeps instead of eating humans. This also means her strength as a demon is based on her will to protect rather than feed.
This also explains why Muzan is after her, he wants to devour her in order to gain the ability to walk in the daylight. Muzan has been looking for centuries of a demon that can conquer the sunlight. After Muzan discovers Nezuko's ability, he decides to change his plans and pursue her for himself.
Muzan, the King of Demons, is the strongest and also the primal demon in the world of Demon Slayer. Consuming his blood is enough to turn you into a powerful demon. He can control all the demons in existence, with only people with strong willpower like Nezuko being an exception.
It is theorized that Nezuko was able to conquer the Sun because she comes from a lineage of Sun Breathing users and because she kept a big part of her own humanity i.e. because she never ate human flesh.
The particular color of her hair would also be reminiscent of her family's history as Children of Fire, explaining the burnt red tinge at the ends of her hair. This implies that Nezuko's hair color represents the demon blood within her; as the color takes over her hair, she may succumb to her demon side more often.
In episode 6 of Demon Slayer season 2, Nezuko entered a berserk state to protect her brother Tanjiro, causing her body to develop into that of an adult. She loses her gag, grows a single horn and gains vine-like patterns across her body.
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.
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.
He was plagued by health issues even in his mother's womb, and was stillborn as a result, but Muzan fought for life and began crying for the first time as his family was about to cremate his body.
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.
Eventually Zenitsu and Nezuko would marry and start a family as evidenced by their descendants.
However, the trait that sets her apart from all other demons is the fact that she has the ability to conquer the sun, prompting the Demon King to call her the "chosen demon". Abnormal Demon Physiology: As the "chosen demon", Nezuko has several unique demonic traits that set her apart from all other demons.
Muzan Kibutsuji (鬼舞辻無慘, Kibutsuji Muzan) is the main antagonist of the Demon Slayer: Kimetsu no Yaiba fantasy action manga and anime series. Muzan is the powerful King of all the Demons, who has the ability to inject his victims with blood that allows him to convert them into more Demons.
And the Wind Hashira, Sanemi Shinazugawa, draws his sword against Nezuko…
Muzan can't control two powerful ladies
According to Comic Book Resources, since Nezuko is able to cling to the humanity she has left, she's also able to block out Muzan's influences. The second demon that Muzan can't control is the kind and smart Tamayo (Maaya Sakamoto and Laura Post).
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.