Born to a Choshu samurai family, he studied at Yoshida Shoin's Shoka Sonjuku and forged a deep friendship with Ito Hirobumi. During study in Britain in 1863 he realized the folly of expelling foreigners; on learning of the outbreak of the Shimonoseki War he hurried home and worked to negotiate a ceasefire. After the Meiji Restoration he joined the Finance Ministry, taking the lead in building modern fiscal institutions. He held key posts including Finance Minister, Foreign Minister, Home Minister, and Minister of Agriculture and Commerce. As Foreign Minister (1879-1887) he pursued treaty revision to abolish the unequal treaties; his Rokumeikan diplomacy—Westernizing Japan to win recognition from the great powers—was glittering but ended in resignation after the treaty revision failed and public criticism mounted. He remained influential in political and business circles and was known for close ties with the Mitsui conglomerate. He died on September 1, 1915, at seventy-nine.

A pragmatic and action-oriented realist who skillfully leveraged his networks in politics and business. His friendship with Ito Hirobumi lasted a lifetime, symbolizing the cohesion of the Choshu clique.

His work building Meiji fiscal institutions and his pursuit of treaty revision laid the groundwork for later achievements. The Rokumeikan remains a symbol of Meiji civilization and enlightenment.