Medama-Oyaji, once a member of the Ghost Tribe, succumbed to a rotting disease that left his spirit bound to a surviving eyeball. This remnant evolved into a diminutive humanoid form, driven by devotion to his posthumously born son, Kitarō. In life, he sustained his family by selling his blood, unwittingly imbuing recipients with ghostly traits. Renowned for his mastery of yōkai lore and occult phenomena, he mentors Kitarō, mediating conflicts between humans and supernatural forces. His malleable body stretches, withstands trauma, and detaches his eyeball to possess objects or scout areas. A fastidious nature compels frequent baths in teacups or bowls, a quirk consistent across adaptations. In *Yo-kai Watch Shadowside: Oni-ō no Fukkatsu*, he aids protagonists against the Onimaro threat, emerging abruptly from Kitarō’s hair to unsettle unprepared allies. His cross-media roles often position him as a bridge between yōkai and humans during crises. Historical ties to Enma, ruler of the underworld, and his Ghost Tribe lineage cement his authority among supernatural hierarchies. Though fragile in appearance, he regenerates from crushing blows or submersion. Some adaptations briefly depict his pre-decayed state as a bandaged mummy or shrouded figure, though the eyeball form remains definitive. Interactions with figures like Nezumi-Otoko reveal patience tested by duplicitous allies, while his bond with Kitarō balances paternal protectiveness with tactical guidance. Spin-offs expand his role to mentor new protagonists, forging alliances against threats like viral yōkai outbreaks or interdimensional dangers. While central to Kitarō’s journey, his adaptability across narratives underscores a legacy as both guardian of occult wisdom and emblem of enduring paternal sacrifice, retaining core traits while navigating diverse challenges.