Medama-Oyaji, also known as Eyeball Father or Daddy Eyeball, originated as a member of the Ghost Tribe. He contracted an incurable "melting disease" while living in seclusion with his pregnant wife Iwako. To support them, he sold his blood, inadvertently causing transfusion recipients to resemble ghosts and attracting unwanted attention. After both he and Iwako died from illness, their son Kitarō was born posthumously from Iwako's grave. Medama-Oyaji's spirit willed itself into his last intact body part—his eyeball—transforming him into a small, anthropomorphic eyeball with a tiny attached body, enabling him to watch over his son. Before his decay, he appeared as a large adult, often bandaged like a mummy due to his illness. The 2018 anime depicted a healthier, human-like form with gray hair covering one eye within a dream sequence, potentially reflecting his self-image rather than historical accuracy. Post-decay, he retains his single, large eyeball head and minimalistic body, typically unclothed. His diminutive size contrasts with his immense spiritual presence, granting resilience against extreme physical damage like crushing or deep-frying, with full regeneration capability. His abilities differ between pre- and post-decay states. As a full Ghost Tribe member, he wielded formidable combat skills, including the Finger Guns technique (Yubi Teppo), firing concentrated spiritual energy and later taught to Kitarō. Post-decay, he relies on body manipulation and possession, such as substituting into empty eye sockets to restore vision or controlling substances like mochi to attack adversaries. He retains the Finger Guns ability even in his eyeball form, delivering exceptionally potent blasts despite his size. His most notable power is summoning the Phantom Train (Maboroshi no Kisha), a mystical transport capable of time travel, though invoking it costs his life due to a supernatural decree. Medama-Oyaji's personality centers on paternal devotion and encyclopedic knowledge. Having traveled extensively before Kitarō's birth, he accumulated vast expertise on yōkai, their weaknesses, and occult lore, positioning him as Kitarō's primary advisor. He maintains personal connections with figures like Enma-Daiō, ruler of the afterlife. His fastidious nature manifests in a fondness for bathing, often in teacups, bowls, or unconventional liquids like sake or cola. He consumes minimal sustenance, such as morning dew or fish-eye soup, reflecting his ethereal biology. Despite comical quirks, he harbors guilt over his diminished form, believing it forced Kitarō into premature responsibility, a theme explored in the 2018 anime. Across adaptations, his role evolves. Earlier portrayals emphasize anxious, doting parenthood, while later iterations incorporate humor, such as his fear of fireworks or television habits. His stance on Kitarō's relationships fluctuates; he sometimes supports human connections but generally discourages them due to humans' shorter lifespans. In spin-offs like Hakaba Kitarō, he adopts a harsher, more cynical demeanor, frequently clashing with Kitarō and Nezumi-Otoko. The 2018 anime delves into his emotional conflict regarding his physical limitations, contrasting his former strength with his current reliance on Kitarō. In the film Gegege no Kitarō: Yōkai Tokkyū! Maboroshi no Kisha, his Phantom Train ability proves pivotal. The narrative reimagines elements from earlier series arcs, centering on the train's summoning and its life-forfeiture consequence, underscoring his sacrificial love for Kitarō.