徳川家斉
The hereditary "daimyō" was head of the clan and head of the domain. In Ōhama, the sole "daimyō" of Ōhama was Mizuno Tadatomo. Tadatomo had been a high-income hatamoto with holdings in the Saku district of Shinano Province He was a page and later an assistant to the 10th "shōgun", Tokugawa Ienari. In 1768, Mizuno became a head of the han of over 10,000 "koku".