In One Piece episode 856 "The Forbidden Secret! Katakuri's Merienda!", the cooks who bring Katakuri's lunch say that no one has ever seen Katakuri while he is eating, and her sister Brulee says that he has never once been on his back since he was born. But when Luffy breaks the house made of Mochi by Katakuri, it is seen that he was lying on his back and eating with his big mouth.
So, what happened to Katakuri's mouth that it is so big and horrifying? Why does he hide his mouth and also from everyone while he is eating? Why does he murder the cooks when he is exposed by Luffy?
Relevant YouTube video: Katakuri True Face, Luffy Exposes Him