Nezuko's actions may sound odd to the uninitiated as she speaks through a muzzle that was put on her when she started becoming a demon. While other demons have gotten used to it, she is still very much adjusting to her new form. Nezuko has the muzzle by her mouth, so she wont just go wild and let her urges to eat humans overwhelm her, shes also gotten used to the muzzle and is okay with having it on, she looks like a normal human, but uh.... Shes a demon, there isnt any additions to it