Up until episode 17 of Kimetsu no Yaiba, we see Nezuko no longer act like the flesh-hungry demon she was when she first transformed, this is for a couple of reasons that I can think of:

  1. She found her senses and understands family is a priority (as shown in ep. 1)
  2. In her 2+ years nap, her anatomy shifted (described by the doctor & mentor), to the point where the hunger is no longer killing her and she can act (somewhat) normally

But given these, why does she still need the mouthpiece? What's its purpose? Also if she did still have the hunger, and it was being used as a preventative, couldn't Tanjiro ask the doctor to make her be able to survive on only blood?

Something doesn't add up.

  • 1
    additionally many other demons Tanjiro has faced can hold conversations and not just mindlessly eat.
    – Rapitor
    Sep 9, 2019 at 18:19

1 Answer 1


Remember that the main thing that Tanjiro is trying to do is find a way to turn Nezuko back into a human. Also, at this point Nezuko is unique because she's the only known demon who has never tasted human blood - even Tamayo and Yushiro rely on allegedly humanely-sourced blood to survive - and it is strongly suggested that this makes it more likely that she can be turned back.

Additionally, Urokodaki used hypnosis on Nezuko when she was sleeping to make her see demons as the enemy and humans as friends. It's not clear whether this is a long-term solution, or if there's a chance that it could wear off at some point. If it does, and Nezuko winds up biting a human, then not only would she potentially be un-saveable, but he and Tanjiro would be bound to kill her as per his promise to the Demon Slayer Corps.

Therefore, Nezuko wears the muzzle to ensure that she never has a chance to taste human blood, either because the hypnosis wears off or just through random chance (for example, in the heat of battle she could wind up biting someone or just getting blood splashed in her mouth from someone's wound).

  • 1
    i get what youre saying but that seems like a long shot out of nowhere while Tamayo couldve made a permanent solution definitively -- (also this brings up the question of why not inform the DS corps of tamayos abilities (SEEMS IMPORTANT)) -- note ill add the bounty but it says i have to wait 4 more hours
    – mshlis
    Jul 29, 2019 at 2:01

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