Nezumi Otoko is a half-human, half-yōkai hybrid with a rodent-like appearance, marked by jutting buck teeth, twitching whiskers, and a scraggly patch of hair atop his head. His notoriously poor hygiene—boasting centuries without bathing—leaves his skin riddled with ringworms and scabs, emitting a pungent odor potent enough to overwhelm bystanders. He typically dons a long brown cloak over a loincloth, though early iterations featured shifting facial structures and attire variations. Born over 300 years ago, his origins remain ambiguous: one account depicts him as a human infant mysteriously appearing on a rat-infested island, while another posits his birth in a liminal realm between the living and spirit worlds, where "Nezumi Otoko" denotes a species rather than an individual. His true name, Peke Peke—derived from a New Guinean term for excrement, underscoring Shigeru Mizuki’s dark humor—is unveiled in the *Kitarō Jigoku Arc*. He shares sparse familial ties with a sister, Nezumi-Onna, and a nephew, Nezumi-Neko. Claiming credentials from Bizarre University’s "Filth Department" with a doctorate in "Lazy Studies," he devises schemes for profit, masquerading as a yōkai researcher, detective, or Kitarō’s agent. His arsenal includes noxious breath, flatulence bursts forceful enough to launch him airborne, and slaps accompanied by the "BiBiBi" resonance from his vibrating whiskers. Though cowardly and prone to betrayal, he displays sporadic resourcefulness, operating machinery or piloting antique vehicles. His relationship with Kitarō hinges on paradoxical symbiosis. While frequently betraying Kitarō for gain, he relies on him for protection, addressing him with informal nicknames like "Kita-chan." Moments of unexpected loyalty surface—risking his life against threats like Wanyūdō or returning swindled funds when confronted. This duality serves Mizuki’s social critique, juxtaposing Kitarō’s selflessness against Nezumi’s opportunism. The 1996 anime tempers his edges, depicting increased cooperation with Kitarō, often to impress human allies like Yumeko. Vulnerabilities emerge: yōkai mourn him at a funeral despite habitual disdain, and he briefly pursues honest labor for a fraudulent "brother." His dread of cats, particularly Neko-Musume, fuels recurring comedic or hazardous clashes. Sporadic lore hints at attending Yōkai Academy with Kitarō and colluding with Shinigami on assisted suicide plots. Fleeting introspection—lamenting loneliness or regrets regarding Neko-Musume—adds depth to his roguish facade. Mizuki frequently deploys him beyond *Kitarō* narratives, including as a narrator in historical contexts, solidifying his role as a complex antihero.