Tokugawa Ieharu
was the 5th Matsudaira "daimyō" of Matsumoto Domain and 10th hereditary chieftain of the Toda-Matsudaira clan. Mitsuyoshi was the 8th son of Matsudaira Mitsuo and was adopted as heir to his brother, Matsudaira Mitsumasa in 1774. He was born at the clan's Gofukubashi residence in Edo. He was received in formal audience by Shōgun Tokugawa Ieharu the same year. In 1777, Matsumoto Castle was destroyed by a fire, and he was forced to apply to the shogunate for a loan of 5000 "ryō" for rebuilding. He died at the clan's Gofukubashi residence in Edo in 1786. His wife was a daughter of Abe Masatoshi of Oshi Domain.