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.
However, frightening as Kibutsuji's blood curse is, it isn't infallible. There are at least two demons in Demon Slayer who have managed to overcome the curse through sheer willpower: Tamayo and Nezuko.
Nezuko broke her ties to muzan by not eating ppl. So muzan has no curse to abuse. This wasn't explained in the anime, but Nezuko was able to remove the curse of Muzan on her own way, just like what Tamayo (Demon doctor) did. This was when Tanjirou and co.
Muzan had attacked Tanjiro's family and shared his blood with Nezuko. This is confirmed when Tanjiro catches Muzan's scent in the city.
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.
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.
Even 400 years later, Muzan's fear of Yoriichi remained fully intact, as simply laying eyes on Tanjiro's hanafuda earrings caused him to recall their clash.
Nezuko becoming a demon was technically planned in that she was another one of Muzan's experiments, but the type of demon she would become would surprise everyone.
Haruka Shiraishi: Muzan's Daughter.
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.
Curse of Kibutsuji
This curse besotted any who partake of Muzan's blood must be careful. 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.
Don't go! DON'T LEAVE ME HERE! Muzan speaks his final words as he loses control over Tanjiro.
Nezuko broke her ties to muzan by not eating ppl. So muzan has no curse to abuse. This wasn't explained in the anime, but Nezuko was able to remove the curse of Muzan on her own way, just like what Tamayo (Demon doctor) did. This was when Tanjirou and co.
Fun fact: The reason why Enmu was able to say Muzan's name out loud without dying is because they're married!
reason why Nezuko can't heal him because his illness is . not based on some demons blood demon. art. It's actually a curse the Ubuyashiki family is stricken with because Muzan.
Nezuko is at least stronger than Daki, meaning that if Muzan could bring her back under his control, she would certainly qualify for the most prestigious title a demon can hold: a member of the Twelve Kizuki. Thanks to Nezuko's remarkable strength, she would have to be an Upper-Moon.
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.
Yoriichi was incredibly proficient in his Sun Breathing, being able to take down demons effortlessly and even overwhelm the Demon King and strongest Upper Rank.
Hoshiko Kibutsuji. The first female demon [of a different orgin], and the younger sister to Muzan Kibutsuji. She loves her brother and was the one who had attacked that man who wore the hanafuda earrings.
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.
Muzan's ultimate goal is to attain an immortal body. He wanted to be able to walk in the sunlight and live forever. In order to gain this, he needed two things: the Blue Spider Lily and the body of a demon who could withstand the sun.
Her final human transformation occurs in Chapter 196 of the manga. Ultimately, Nezuko survives and finally turns into a human after being stuck as a demon for so long. Despite turning into a human, she's one of the prime reasons why Tanjiro could defeat Muzan, even after almost being turned into a demon himself.
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.
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.
However, Tanjiro is not a descendant of Yoriichi Tsukiguni. Tanjiro is the descendant of someone who knew Yoriichi personally and was a good friend of his as well. Sumiyoshi was rescued by Yoriichi when a demon threatened his life. Since then Yoriichi often met him and they became close acquaintances.