Medama Oyaji originated as a fully-formed adult member of the Ghost Tribe afflicted by an incurable melting disease. While living in seclusion with his pregnant wife Iwako, he sold his blood to survive, inadvertently causing transfusion recipients to resemble ghosts. This drew blood bank investigators, leading Medama Oyaji to reveal his story to an investigator named Mizuki and request discretion. Both Medama Oyaji and Iwako succumbed before their child's birth. Motivated by profound paternal love, he willed his spirit into his last intact physical remnant—an eyeball—after his body decayed, resulting in his signature appearance as an anthropomorphic eyeball with a diminutive body. His son Kitarō was subsequently born from Iwako’s grave. Physically, he manifests as a giant eyeball with a small, typically unclothed body. His eyeball head features a functional eyelid (depicted as a simple line over his pupil) and a rarely visible small mouth beneath the eyeball that retracts at will; he possesses no teeth but can extend this mouth outward when needed. Early portrayals rarely showed him eating, though later adaptations depict consumption of items like cherries, plums, fish eye soup, and morning dew. His body exhibits remarkable resilience, regenerating instantly after being crushed, flattened, or even deep-fried, always returning to his original form. He and Kitarō can endure up to a decade without sustenance. His abilities include body manipulation, eyeball substitution, and extensive knowledge of yōkai lore acquired during travels before Kitarō’s birth. This expertise encompasses nearly all yōkai types, their weaknesses, and broader occult subjects like Akuma or ancient civilizations. His spiritual connections grant direct access to figures like Enma-Daiō (the king of hell), enabling travel between realms for mediation or requests. Medama Oyaji prioritizes hygiene, often bathing in small containers like teacups, bowls, or unconventional vessels filled with liquids such as black tea, coffee, sake, sand, or cola, reflecting his enjoyment of cleanliness and comfort. His personality centers on unwavering devotion to Kitarō, supporting him through guidance, historical knowledge, and occasional matchmaking efforts—such as encouraging Kitarō to explore romance via a dating simulator. He also demonstrates deep loyalty to his deceased wife, Iwako. Despite his comical appearance and habits, his spirit is characterized by tenacity and paternal protectiveness. Within the broader franchise, Medama Oyaji consistently serves as Kitarō’s advisor and emotional anchor, leveraging his Ghost Tribe heritage and supernatural network to resolve conflicts involving humans or malevolent yōkai, emphasizing familial bonds and coexistence between worlds. Regarding the specific work *Gegege no Kitarō: Gekitotsu!! Ijigen Yōkai no Daihanran* (1986), no unique character development or plot-specific details beyond his established traits are provided.