Kaiman

Kaiman 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, his main goal is to seek out the one who cursed him in order to change himself back. Because he can't remember who cursed him, due to his amnesia, he instead resorts to clamping his mouth around the head of every magic user he comes across, letting them see the "little man" in the back of his head before pulling them back out so he can ask them all the same question: "What did the guy inside my head say?"

Throughout most of the series, Kaiman, true to his moniker, takes on the appearance of a lizard-like entity. Though his body is consistently human with a tall and muscular build, his face and head have changed dramatically due to the effects of a Magic User. He most closely resembles a Caiman lizard, (though some think he looks more like an Iguana) his hair being replaced by long, very sharp spikes. It appears that despite having his head chopped off, he can regenerate it in a few days time. He sports small crosses over his eyes and wears gas masks most of the time, though he refrains from wearing them later on in the series.

Kaiman usually takes on the personality of someone arrogant and lazy, but deep inside he's rather caring and cares a lot for his best friend, Nikaido. Rude, stubborn and prone to resolve anything with violence, there's a few things in Kaiman's mind and heart, wishing to have his normal head back, eat gyoza and having more money (in that specific order); only caring about subjects related to those three things and showing no regard or concern about anything else. He sees Magic Users as scum, killing them in the spot after interrogating them and showing no remorse for that, he hates them and he even would start a mass slaughter in the middle of their realm to find the one responsible for his head. He has constant nightmares about his creation and death, causing Kaiman to wake up tired, worried, scared and trying to forget them, even if sometimes they have a connection to his past. He has shown to be easily distractible as during both his jobs he finds himself easly distracted by things.

Kaiman does eventually get his human face back, along with his lost memories, but the truth about his identity was more than he bargained for. It turns out he was originally a human boy from Hole named Ai Coleman. Ai put himself through surgeries to become an artificial magic user, and his self has since fragmented into several quasi-independent personalities attached to multiple heads, including Aikawa and Kai. Kaiman actually wore one of Kai's heads for most of his time in Hole, as indicated by the crosses he had around his eyes. He switched to Aikawa's crossless head when he experienced a flashback at the Zagan school of magic. Kaiman was still wearing Aikawa's head during his fight with En when Ebisu's reptilian magic was dispelled, which is why he reverted to the Aikawa personality and not Kai at that time.