As a demon, 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. 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 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 in .
Nezuko protecting Tanjiro from Giyu.
Since becoming a demon, Nezuko appears to have become also 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 refusal to consume human flesh or blood, even in cases of extreme injury or exposure to human blood, which can be seen when she refuses 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.
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.
