Kaiman

Caiman is the main protagonist of the manga and anime series. He is a human born in the Hole with an immunity towards magic. He has made it explicitly clear that "Kaiman" was not his actual name, but was given to him by Nikaido after he began suffering from amnesia. His lizard head being the result of a Magic User's curse, and his main goal to seek out the one who cursed him in order to change his face back. But, because he can't remember who cursed him, Kaiman resorts to clamping his mouth around the head of every Sorcerer he comes across. He lets them meet the "man" in the back of his mouth ...