However, she wasn't immune to the sunlight initially, as she got burned badly at first. So, in conclusion, her coming from a Sun Breathing user's lineage and not relying on human substance are perhaps the reasons for her immunity.
Sunlight: The greatest threat to nearly all demons is sunlight, which ignites their cells, severely limits their regeneration, and fatally burns them to ashes. The only demons so far to have developed resistance to sunlight are Nezuko Kamado and Tanjiro Kamado.
If Tanjiro stayed a Demon, all of the other characters who survived (Sanemi Giyuu, Kanao, Zenitsu, Inosuke) would of all been killed by the Demon King. Tanjiro at that point had become immune to the sun and as a Demon was already immortal, literally nothing was able to contend with him.
Muzan can't control two powerful ladies
One of the demons he can't manipulate is Nezuko (Akari Kitō and Abby Trott), the half-human sister of Tanjiro. 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.
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, 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.
While she might not be as powerful as Muzan himself, her overall strength makes her easily comparable to an Upper rank demon.
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.
The curse prevents Muzan's name from being spoken aloud, and any who do will meet a horrible demise. One demon, Susamaru, faced this reality when battling Tamayo. Susamaru accidentally shot Muzan's name aloud, attempting to defend his honor with her mind clouded.
8 Tanjiro Is The Only Living User
On the other hand, Sun Breathing can, presently, only be performed by Tanjiro Kamado. Though its techniques can be taught to others provided they have the guidance of a Kamado, there are no other known users who are currently alive.
Abnormal Demon Physiology: As the "chosen demon", Nezuko has several unique demonic traits that set her apart from all other demons. Most notably, Nezuko can continuously restore her power without consuming any human blood like any other demon would need to do.
The last user is Tanjiro Kamado, who learned the Breathing Style from his father, Tanjuro Kamado. Other people can learn this technique if taught by a Kamado descendant.
8) Muzan hates being called pale or dead
Muzan is the most powerful demon in the entire series, and is responsible for creating all demons. For someone who considers himself to be perfect, it is natural that he will hate being called pale or dead. This is established quite early on.
Apart from Tanjiro, the show centers on his younger sister Nezuko Kamado, turned into a demon by Muzan Kibutsuji. Demons are incapable of walking out in broad daylight because the sunlight will burn them into the ashes. However, Nezuko has immunity against the sun, so she was given the name “The Chosen Demon”.
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.
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.
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.
Technically, the elder of the two Sakuras` was actually Muzan`s child, by way of his mistress (Lady Jade Wong), who had one of her eggs inserted into Anne`s body.
With this in mind, if Nezuko had also been murdered by Muzan, Tanjiro would have no reason to be empathetic toward demons. Her transformation gave him a perspective of both demons and humans, but without Nezuko becoming a demon he would have no reason to take their feelings into account.
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.
In conclusion, Nezuko cannot beat Akaza in Demon Slayer. In terms of power, physical abilities, regeneration rate and overall combat ability, Akaza is far superior compared to Nezuko.
However, in truth, as revealed after her death, Muzan sees Daki as a tool to keep her brother, Gyutaro, in line, deeming her to be the main reason why the "true" Upper Rank 6 was killed and in truth does not think highly of her and deeming her as someone not very intelligent.
Akaza. Because of his desire to become stronger and Doma's strength allowing him to surpass himself to become Upper Two, Akaza harboured an intense hatred of Doma.
Tsukito, Yorogi, Kuraku, and Isatsu all agree that they are loyal to Muzan.