Lord of the Karatsu Clan in Kyiishii, he was commonly called Keishichiro. Eldest son of Nagamasa. Went to Edo (1838) and became well known for his perspicacity. In 1857, he became the son-in-law of Nagakuni Ogasawara and ably ruled his clan for four years. After returning to Tokyo (1872), he spent his remaining years in quiet seclusion.
Was promoted by the Shogunate to Waka toshiyori (Shogunate Vice-Minister) (1862) and took charge of foreign affairs. Late in that year, he went to Kyoto and solved many difficult problems. Returned to Edo (1863) to negotiate with Britain on the Namamugi Incident in which a Briton was killed and two others wounded by samurai of the Sarsuma Clan. He paid an indemnity of 100,000 pounds to Britain at his own judgment and ordered that all ports be closed to foreign shipping. Then, accompanied by Shogunate soldiers, he boarded a British warship and proceeded to Osaka to explain to the Court the circumtances that had led to the payment of the indemnity. The Court prohibited his visit to Kyoto and he was confined at the residence of the commander of Osaka Castle. Although the Shogunate punished him for his arbitrary action concerning the Namamugi Incident with house arrest, he was reinstated (1864) and was appointed Raju or Minister (1865). He commanded the Shogunate expeditionary forces against the Choshii Clan (Yamagu chi Prefecture) (1868). Returned to Edo at the report of the death of Shogun Iemocllj. He was discharged but was appomted Raju again and then Director General of Foreign Affairs. He opened Kobe port to foreign ships. At the Meiji Restoration (1868), he together with Keisuke Oiori, resisted Imperial forces at Goryokaku Fort at Hakodate, Hokkaido.
