Yeah, it goes like this (since Kitaro's Origin Story has been more or less the same for fifty years now, I figure this ain't a spoiler since it's on the level of "Peter Praker gets bit by a radioactive spider and becomes Spiderman"): Oyaji and his wife were the last of the Ghost tribe. Both, however, were elderly, and both died shortly before Kitaro was born. Kitaro's mother was buried, and he was a literal "coffin birth" that then escaped from the grave. Out of worry for his newborn son, Medama Oyaji tried to return to life, but at this point he was so rotted that all that was left was his left eyeball, which became Medama Oyaji. Kitaro and him were then taken in by a human who helped raise Kitaro for a time.
