Why Can't Nezuko Talk

Why is Nezuko silent?

Most importantly, Nezuko upholds a vow of silence by remaining mute throughout the series. 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.

Does Nezuko speak?

Initially, she is unable to speak and must wear a bamboo gag to keep from biting anyone. However, in later volumes, the muzzle is removed and she gains the power of speech, albeit very broken due to not speaking for more than two years.