Lord of the Uwajima domain (Ehime Prefecture) and statesman. Born as the son of YAMAGUCHI Sagami no Kami Naokatsu, a vassal of the shogun, in 1829 he was adopted by DATE Munenori, the lord of the Uwajima domain. In 1844, he became the lord of the domain and devoted himself to Fukoku Kyohei (enriching the country and strengthening the military), and Shokusan Kogyo (encouragement of new industry). In 1858, he retired from his position as a feudal lord, but as an adviser to the shogunate, he advocated Kobu-gattai (reconciliation between the imperial court and the shogunate), and met with the British Minister to Japan, Harry Parkes. After the Meiji Restoration, he assumed the post of Gijo, and served in foreign diplomacy positions, such as the governor of foreign affairs and foreign governor. In 1871, he signed the Japan-Qing Treaty of Friendship as Foreign Minister Extraordinary. He hosted King Kalakaua of Hawaii and was awarded a medal in 1881.