The Katō clan (加藤氏, Katō-shi) was a samurai and aristocratic clan in Japan. It was said that the Ka in Katō came from the Fujiwara clan of Kaga. Katō Kiyomasa came from the Katō clan, who claimed to be descendants of the Fujiwara-Kitaoji clan. Katō Mitsuyasu and Yoshiaki were descendants of the Fujiwara-Kitaoji clan. The latter two branches became the lords of Ōzu and Minakuchi respectively in the early modern period, and after the Meiji Restoration, both clans were ennobled as viscounts.[1]
Since the Sengoku period, the Kato Mitsuyasu line has been prominent. Katō Mitsuyasu served under Toyotomi Hideyoshi and was granted the Kai Province of 240,000 koku.[4] His son, Katō Sadayasu, was reduced to 40,000 koku in Mino Province in 1594,[5] and then transferred to the Yonago Domain in 1610, where he received an additional 20,000 koku, totaling 60,000 koku.[6] In 1617, he was transferred to the Ōzu Domain. The domain continued until the abolition of the han system. The last lord, Katō Yasuaki, was appointed as the governor of the Ōzu Domain in June 1869, during the abolition of the han system, and served as the governor until the abolition of the han system in July 1871.[7]
When he was transferred to Mibu Domain in Shimotsuke Province, he was granted an additional 5,000 koku, and after being returned to Mizuguchi Domain in 1713, the same domain continued to exist until the abolition of the han system. The last daimyō of Minakuchi Domain, Akihisa, was appointed as the governor of Minakuchi Domain in June 1869, and served as the governor of the same domain until the abolition of the han system in July 1871. With the integration of court nobles and daimyo families in the administrative officials on June 17, 1869, the peerage system was established, and the Kato clan was also listed as a peerage as a daimyō clan. When the peerage system became the five peerage system with the enforcement of the Peerage Law on July 7, 1884, he was listed as a viscount August 8, 1884 as a former small han governor.[8]