Nyanko-sensei, truly the powerful yokai Madara, manifests in two distinct forms. His frequent guise is that of a rotund, white maneki-neko adorned with orange and grey markings on head and back, featuring black eyes, a red collar with a gold bell, and small red facial markings. Ordinary humans perceive only this form, mistaking him for an overweight house cat. His true self is a colossal, wolf-like yokai with white fur, red facial markings, and golden eyes, large enough to conceal a human under one paw. This beast form possesses a significantly deeper voice and remains unseen by humans without spiritual perception. Once a high-ranking, widely feared yokai, Madara was sealed decades ago inside a maneki-neko statue by an unknown powerful exorcist. He remained imprisoned within a forest shrine until accidentally freed by Takashi Natsume, who tripped over the sealing rope while fleeing another yokai. Madara shares a history with Takashi's grandmother, Reiko Natsume, having interacted with her multiple times. He maintains Reiko never defeated him in a challenge, so his name was never added to her Book of Friends. Initially attacking Takashi to seize the Book, Madara relented upon learning Takashi cherished it as a connection to Reiko. He proposed a pact: acting as Takashi's bodyguard and spiritual advisor in exchange for inheriting the Book upon Takashi's death. This agreement led Madara to reside with Takashi at the Fujiwara household, posing as a pet cat nicknamed "Nyanko-sensei" by Takashi, though Madara insists he is the master. Others assign him nicknames like "Ponta" (Tanuma), "Nyankichi" (Touko Fujiwara), and "Nyangoro" (Shigeru Fujiwara). Madara exhibits a proud, condescending, and frequently comedic personality. He vocally complains about Takashi's excessive kindness yet demonstrates a fondness for human comforts, particularly food, drink, Japanese sweets like dango, seafood, and copious sake, habits contributing to his round physique. Despite vehemently denying feline nature, he displays cat-like behaviors: chasing small animals, playing with cat toys, bullying dogs, and frequent napping. He is easily enticed by food offers as payment for assistance. Though initially motivated solely by obtaining the Book, Madara gradually develops a deep, often unacknowledged attachment to Takashi. He becomes fiercely protective, intervening against threats without summons. This protectiveness extends to the Fujiwara household, motivated partly by his enjoyment of living there and eating Touko's food. Instances like guarding the home from the yokai Kayatsubo or expressing regret that Takashi didn't become immortal demonstrate his growing care, which he typically downplays with selfish justifications. He maintains a mentor role, educating Takashi about yokai and the spiritual world. His relationships with Takashi's friends are complex: he tolerates Kaname Tanuma but actively avoids Tooru Taki due to her enthusiastic embraces. He harbors deep distrust towards exorcists Shuuichi Natori and especially Seiji Matoba, whose sinister aura he detects. As a high-level daiyokai, Madara commands immense spiritual power, widely respected and feared among other yokai. His abilities include flight despite lacking visible wings, shapeshifting between cat and beast forms, and assuming human disguises (primarily resembling Takashi or Reiko, though imperfectly mimicking their personalities). He can project a powerful spiritual light ray from his forehead marking to destroy or repel yokai, summon thunderclouds and lightning strikes even in cat form, and remains largely immune to standard exorcist charms and barriers. His strength is exponentially greater in his true beast form. He possesses extensive knowledge of the spirit world and its history.