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.
When fighting the Upper Six demon Daki, sadly, Tanjiro found himself outmatched, but out from her box came Nezuko with a kick. She started going off against Daki and had her body severed several times. She then transformed, due to the fight, into her adult demon form and grew into … well, a busty demonic woman.
Due to her demon abilities, Nezuko can change her size/age and appear “mature” in a slightly older form or can even make herself look younger and smaller than a 12-year-old. Anime is weird and demon stuff only makes it weirder.
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.
While Nezuko slept and Tanjiro trained with Urokodaki at the beginning of the series, two years had passed, which means that, while Tanjiro would go on to turn 15, Nezuko became chronologically 14-years-old, though still technically a 12-year-old.
A few episodes later, Nezuko is 14 years old, however, physically, she has not aged since that faithful and tragic day, and that's something that will not change unless Tanjiro finds a cure.
While she might not be as powerful as Muzan himself, her overall strength makes her easily comparable to an Upper rank demon.
Tanjiro is ready to do anything, even die, if it means saving his sister. It becomes clear that Tanjiro's only choice is to join the Demon Slayer Corps himself and despite the intense, dangerous training, he doesn't hesitate. He loves Nezuko more than he fears demons or even death.
The muzzle serves as a representation of Buddhist practices. First, it gags Nezuko, preventing her from speaking like a Buddhist monk's vow of silence, but it also is there to suppress her desire to eat humans. Through a Buddhist lens, Nezuko's muzzle is the symbol of a Buddhist monk.
Nezuko Kamado
Despite having an intense fear of Demons, Zenitsu develops a crush on Nezuko. He tries to convince her to marry him several times and never fails to mention his admiration for her whenever he sees her.
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.
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.
Nezuko is 12 to 14 years old in Demon Slayer, and she does not die. Rather, she helps her brother, Tanjiro, wage war against the demons and also turns back into human form.
Weakness: Weaknesses associated with Demon Physiology, however the weakness to sunlight was eventually overcome. Nezuko's flames appear to only work on Demons and demon-based abilities, while harmlessly affecting humans. Using too much blood for her Blood Art can make her fall asleep.
Of course, Nezuko never consumed any human, so Daki initially thought that she wouldn't be able to regenerate. However, Nezuko quickly restores her body parts, which obviously comes as a shock for Daki. After that, Nezuko transforms into her Berserk Demon form, which is also called her "Awakened Form."
Nezuko and Kito also share the same height, 5'0".
The now-iconic bamboo muzzle serves as a way of stopping Nezuko from using her teeth, and also keeps her from tasting human blood, which would cause her to lose control of herself.
However, in later volumes, the muzzle is removed and she gains the power of speech in volume 22 then remembers everything and gets her human thoughts again and remembers her name, albeit very broken due to not speaking for more than two years.
If Nezuko were to taste blood, it's likely that she would lose control completely, forcing Tanjiro and other demon slayers to kill her. So the bamboo gag really protects Nezuko as well as the other humans the slayers may encounter on their journey.
Demon Slayer's adorable icon Nezuko has stolen fans' hearts for five key reasons, earning her the title “Best Girl” of the series.
Muzan Kibutsuji
Just like Tanjiro, Nezuko shows nothing but hatred towards Muzan. During her battle with Daki , she regained the memories of when Muzan killed her loved ones which convinced her to kill one of his followers as well.
After the battle, Tanjiro returns home with his sister and friends. Later it is revealed that he married fellow slayer Kanao Tsuyuri.
While Tanjiro's attitude to demons may have changed with Nezuko's death, his human relationships would probably remain similar. His anger and compassion could co-exist, which realistically would lead to him making the same connections as he did with Nezuko's companionship.
"Humans are to be protected and saved... I will never hurt them." - Nezuko Kamado.
Nezuko doesn't stand a chance against the Upper Moon 3
She underwent a transformation and thoroughly overwhelmed the Upper Moon 6 demon. That being said, there is absolutely no way Nezuko can even come close to beating Akaza.