Medama-Oyaji, dubbed “Eyeball Father,” emerged from the Ghost Tribe, a formerly influential yōkai clan. After contracting a terminal “melting disease” prior to his son’s birth, he retreated into seclusion with his pregnant wife, Iwako. To support their family, he sold his blood, unknowingly triggering ghost-like transformations in transfusion recipients. This anomaly attracted Mizuki, a blood bank employee, whom he convinced to withhold reporting their situation. Both Medama-Oyaji and Iwako later perished from illness, but his lingering spirit inhabited his surviving eyeball, fueled by devotion to his son, born posthumously from Iwako’s grave. His decayed form manifests as a solitary giant eyeball with a tiny body, typically unclothed but sometimes adorned with accessories like a silk hat or shoe. He conceals a small, seldom-seen mouth beneath the eyeball, enabling consumption of foods such as fish-eye soup or morning dew. Remarkably resilient, he regenerates from severe damage—including crushing or deep-frying—and endures up to a decade without nourishment. His skills encompass body manipulation, eyeball replacement, and vast occult expertise, covering yōkai vulnerabilities, ancient civilizations, and ties to figures like Enma-Daiō, ruler of hell. His narrative role shifts across media while retaining core traits. Early adaptations cast him as a guiding figure chastising Kitarō for impulsiveness. The 1996 series amplified humor, showcasing him exercising, fearing fireworks, and dabbling in modern trends. Though he tentatively encouraged Kitarō’s bond with Neko-Musume, her violent tendencies later tempered his support. The 2018 anime delved into his insecurities about his grotesque form affecting Kitarō’s childhood. A dream-sequence arc briefly resurrected his youthful human guise—a taller, platinum-haired figure mirroring Kitarō in a tattered kimono—though the vision’s legitimacy remains unclear. Spin-offs like *Hakaba Kitarō* align with the original manga’s grim aesthetic, depicting his bandaged, pre-eyeball incarnation as harsher and less paternal. He rebukes Kitarō’s apathy toward their lineage and conflicts with allies like Nezumi-Otoko. The 2023 film *The Birth of Kitarō: Mystery of GeGeGe* retroactively names his pre-decay identity as Gegerō, solidifying his legacy as the namesake for his son. Beyond Kitarō, he interacts with allies such as Sunakake-Babaa, who verified his past appearance, and Enma-Daiō, whom he entreated for underworld access. Despite eccentric habits like bathing in cola or sake, his steadfast commitment to safeguarding his son and maintaining yōkai-human equilibrium defines his character universally.