2.Personnality :

Nezuko's original personality as a human was that of a kind and caring girl who thought of others before herself much like her older brother, Tanjiro. Additionally, she was a responsible elder sister to her younger siblings and often put their needs first rather than her own. Nezuko is, however, not afraid to get in harm's way, protecting her friends from demons even after being returned to a human state. It is also shown that Nezuko's humane, laid-back demeanor supports this fact after Tanjiro apologized to her.

Nezuko's friendly disposition.

While Nezuko initially starts off like any other demon, bloodthirsty and hungry for human flesh, after seeing her brother’s desire to protect her from being killed by a Demon Slayer despite her being a demon, she changes completely and becomes fiercely protective of him. Unlike most demons who fully remember their human life, Nezuko seems to have forgotten a good portion of her memories as a human, besides those related to her family, and thus doesn't retain the exact personality she had before transformation, instead acting akin of a child. She is still very caring and protective towards humans who she sees as members of her family, although this is mainly due to the influence Sakonji Urokodaki had on her while she was asleep for two years. Nezuko also retains some of her human emotions, as she has been seen to cry when sad and smile when happy, but in general she appears more detached than her human cohorts, although she is still much calmer and less malicious than most demons. Nezuko also tends to see the images of her siblings in other humans, like Rokuta Kamado in Yushiro.

Nezuko protecting Tanjiro from Giyu.S

Since becoming a demon, Nezuko appears to have become rather brazen, and does not seem to fear fighting; she fiercely guards her brother as well as her allies. She has also developed a strong willpower, which can be seen through her fusal to consume human flesh or blood, even in cases of extreme injury or exposure to human blood, which can be seen when she refuses Sanemi Shinazugawa after he attempts to lure her into biting him with his Marechi blood. Her strong willpower remains even when she is no longer a demon, shown when she willingly leaps in front of Inosuke to protect him from her own brother, who had become a demon and was attempting to kill those around him. Though she could have been killed, Nezuko did not hesitate to protect her brother.

On the rare occasion that Nezuko attempts speech, she has been seen to stutter a lot, which may be due to her bamboo mouthpiece, which is seldom removed, and the fact that she didn't speak for a number of years after her transformation. However, after developing resistance towards sunlight, which allows her to go outside and interact with others more often, her speech has shown signs of improvement and she is able to fully pronounce words if someone else has just spoken them, or hears them repeated frequently enough.

It was later revealed by Tamayo that her missing memories and underdeveloped personality were due to her being not fully conscious, as she prioritized developing her resistance to sun to regaining her consciousness.