Yagyou-san is a youkai from GeGeGe no Kitarou who's best known for being an inventor—particularly for creating the Youkai Car. He typically gets around by riding Kubinashi-Uma, a headless horse.
His exact status in the series is a bit fluid. Sometimes he's portrayed as god-like, other times as a high-ranking oni, but the details shift depending on which version you're reading. In Saishinban GeGeGe no Kitarou specifically, he's described as closer to a god than a youkai, and interestingly, he outranked even Nurarihyon despite initially serving under him.
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