Demuncher is a stout humanoid-like Yo-kai with light yellow skin, a golden brown spiral shape on the dome like tip of his head, small offset white eyes, golden brown lips with a scar on his right, and, most notably, large teeth with canines. He wears a large dark turquoise bead necklace, a white robe with a red haori, a hakama of the same color, and sandals with white socks.
He is able to devour any demon unfortunate to be in the way of his jaws. The Boss version of Demuncher seen in Yo-kai Watch 2: Psychic Specters is big enough to eat Oni the size of Gargaros with contemptuous ease. This was also seen in Yo-kai Watch Busters.
In Yo-kai Watch 2, after the second sidequest requested by Master Nyada, which involves a battle with Demuncher, it is revealed that he is a pupil of Master Nyada. Demuncher clearly holds the cat Yo-kai in high regard.
Take the Request: "Nyada's Test Episode 2" after beating the game and meet Demuncher at the top of Mt. Middleton in the past, where you can battle him once a day until he's befriended through the regular method. Befriending Demuncher completes the Request.