Based in the dystopian Hole, Caïman possesses a human body but a lizard head—a result of cursed Ebisu smoke transforming him and causing amnesia. Friend Nikaido named him after his memory loss. His reptilian features resemble a Paraguayan Caiman Lizard: sharp head spikes replace hair, with distinctive red cross marks around the eyes. Early art depicted him lanky with an elongated muzzle; later versions show a muscular, broad-shouldered build and shorter snout. Severed, his head regenerates fully within days, and his skin periodically sheds. Outwardly arrogant, lazy, and violently hostile toward magic users—whom he deems inherently evil—Caïman simultaneously shows deep loyalty and kindness to friends like Nikaido. His core motivations are clear: first, reverse the curse to regain his original head and memories; second, consume gyoza; third, improve his finances. Recurring nightmares of his traumatic creation fuel persistent anxiety and fatigue. He confronts threats directly and brutally, sparing only magic users who refrain from harming humans. Caïman originated as the fourth split personality from Ai Coleman’s body, emerging after Kai—leader of the Cross-Eyes gang—was decapitated by the supernatural "Curse" while using Ebisu’s smoke. This fragmentation left Caïman a blank slate, while trapping the Curse within him. This convergence grants absolute magic immunity, though physical attacks or enchanted weapons can wound him. For two years, he patrolled the Hole with Nikaido, hunting magic users who experimented on humans. His signature tactic: clamping his jaws around a sorcerer's head so the mysterious man residing in his throat cavity could inspect them. Withdrawing, he’d ask, "What did the guy inside my mouth say?" Typically hearing "You are not the one," he executed them instantly, earning the title "Magician Killer." He intermittently worked at Dr. Vaux’s hospital for magic victims but often neglected duties. Key events included maiming sorcerer Ebisu during interrogation; battling En’s enforcers Shin and Noi (losing his head to Shin but regenerating); and discovering his severed head could develop independent consciousness. Seeking curse clues, Caïman traveled to the sorcerers’ world via Professor Kasukabe’s artificial door. Disguised as "Pieman," he interrogated sorcerers while adapting to their culture. A nightmare there recalled the name "Risu"—a vital link to his past—revealing the "man in his mouth" was Risu’s Curse seeking Kai, not Caïman’s curser. He also confronted the conflict of Nikaido being a sorcerer. Later, he uncovered his body’s ties to the Cross-Eyes gang, whose members shared his cross-shaped eye marks. His origin as part of Ai Coleman’s fractured psyche culminated in Kai briefly reasserting control. During the Hole-kun conflict, devils imbued Caïman with immense magic power, manifesting as a wish-granting sentient gyoza capable of offensive/defensive constructs. Briefly wielding this power, he later rejected restoring his original head, accepting his lizard form. His preserved severed head resurrected separately as Risu. Nikaido remains foundational: he prioritizes her safety above most goals. His connection to Risu—as the throat voice and later a separate entity—ties directly to his origins. Alliances with Dr. Vaux and Professor Kasukabe aided his quest.