Third son of Tokugawa Yorifusa and grandson of Tokugawa Ieyasu who was a prominent daimyo with a large influence on the politics of the early Edo Period. He became daimyo of Mito at the age of 34 and compiled a large collection of Japanese history, the Dai Nihon shi, which depicted Japan as one nation under the Emperor, and preceded the rise of nationalism in the late shogunate.