Nezuko is the daughter of Tanjuro Kamado and Tanjiro's younger sister who is turned into a demon Despite Muzan Kibutsuji assumption that he has killed them all in his attempt to sire a sun-resistant demon, Nezuko survives as a demon with her mind mostly gone.
At 14, just a year younger than Tanjiro and Inosuke, Nezuko is very much the baby out of the four. She's also the youngest character in the main cast. Nezuko's short stature makes her look a lot younger than she appears — her wide eyes and diminutive features seem rather childlike.
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.
The reason why Nezuko Kamado acts like a baby now, unlike most demons in the show. When Nezuko was turned into a demon, she went into a childlike state. Other demons just became a darker, twisted version of their past self, minus a few memories.
While stuck physically at age 12 because of the whole demon thing, Nezuko is 14 chronologically.
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.
Sanemi stabs Nezuko's box multiple times, prompting her to leave it. Seeing the Hashira's wounded arm, she is transfixed by the sight of his blood.
After the battle, Tanjiro returns home with his sister and friends. Later it is revealed that he married fellow slayer Kanao Tsuyuri.
Nezuko marries Zenitsu Agatsuma in the Demon Slayer series.
This means that Tanjiro is a more conventional age during the bulk of Demon Slayer's story, at age 15. That's a classic age for shonen heroes like him, with Izuku being 15 when he first enrolled at UA and Bleach's Ichigo Kurosaki being 15 when he first gained the powers of a Soul Reaper.
Since Nezuko is from a Sun Breathing lineage she can survive in daylight. After the final battle against Hantengu concludes she can step into daylight and many theories are available about the phenomenon. One of the theories is that her abstinence from consuming human blood is what saved her.
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.
According to the creator of Demon Slayer, Koyoharu Gotouge, Nezuko's biological age is 12. This means that while she has been alive for 14 years, her body has only aged to the point of a 12-year-old.
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.
Kamado Nezuko (14 years old)
Born on December 28, Nezuko is choronologically 14 years old during the Swordsmith Village arc.
It is confirmed in the Volume 23 extras that Inosuke and Aoi did eventually end up together and that they have two great-grandsons, one of which is Aoba.
Furthermore, to Tanjiro, Inosuke and Zenitsu's surprise, the Sound Hashira has three incredibly beautiful wives.
Even though Nezuko was turned into a demon, she didn't go full dark side. While she is influenced heavily by evil, Nezuko cares deeply about her family and time and again proved that she will do anything to help them when trouble ensues.
Nezuko's ability to keep her head attached to the rest of her body was revealed when she confronted Daki. When the Upper-Rank Sixth used her Obi to slice off Nezuko's head and several other body parts, she was able to manipulate her own blood to keep everything connected.
However, unlike many other characters, Nezuko will not die at the end of the series, but will revert to her human form during the Final Battle arc.
Therefore, it is safe to assume that Zenitsu and Nezuko end up together and have kids in the future. This is proof that Zenitsu loved Nezuko and she too came to love him at some point in time.
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.
Unlike other demons who survive on blood, Nezuko never really needs it, and she doesn't even consume human food either. Moreover, Nezuko has never shown any signs of undernourishment as she is always ready to assist her brother with her overwhelming strength and deadly Blood Demon Art.