He was born as son of OKUMA Nobuyasu who served Saga domain. As his father was an upper-class samurai, he learned at Kōdōkan, school of the domain. However he opposed to the policy of the school and joined the group of royalists around 1855 and learned English on the following year.
In 1865, he established a school of English and was active in royalism. Before it, he tried to mediate between Chōshū domain and the Tokugawa shogunate but failed. In 1867, he left the domain with SOEJIMA Taneomi to advise TOKUGAWA Yoshinobu to return the government to the crown but they were arrested and forced to confine themselves in a house.
After the Meiji Restoration, he was recommended by KOMATSU Tatewaki and was appointed to a judge in Foreign Affairs Bureau. When Sir Harry Parkes criticised the Urakami Yoban Kuzure, the oppression of Christians especially Catholics in Nagasaki, he told him that it's an interference in internal affairs. However some say it influenced the plan of revising the treaties of the Iwakura Mission. He then became vice foreign prefectural governor and remarried Saegusa Ayako.
He later became a councilor and the Minister of the Ministry of the Treasury and promoted the policies of modernising Japan. He also supported Mitsubishi Steamship Company established by IWASAKI Yatarō. And then he insisted on establishing national assembly and party cabinet but later he resigned his position because of the opposition against those from Satsuma and Chōshū.
In 1882, he formed the Constitutional Progressive Party (Rikken Kaishin tō). And he also established Waseda University. In 1887, he received the title of count and was appointed to the Minister of Foreign Affairs. Then he attempted to revise treaties but the idea of introducing a foreign judge met with opposition. Then he was wounded in the right leg by a member of Gen-yō-sha, a political organisation and had the leg amputated. Then he resigned the position. In 1898, he formed the first party cabinet with ITAGAKI Taisuke and became the first Prime Minister from Hizen (Saga) but the cabinet was short-lived.
In 1907 he retired from politics and became the president (chancellor) of Waseda University. Then he published may foreign books translated into Japanese and conducted cultural activities. In 1914, he returned to political world as PM and made a declaration of war against the Germanic Empire (*). In 1916, he retired from politics completely because of the scandal of ŌURA Kanetake, Minister of Foreign Affairs. He died of gallstone in 1922.
It was FUKUZAWA Yukichi, establisher of Keiо Gujuku who encouraged him to establish a school also. Then he established Waseda University. On the other hand he reacted with NIIJIMA Jō (Joseph Hardy Neejima) and agreed with his idea of establishing Doshisha University in Kyoto. It is sais that he never visited Kyoto without giving a lecture. Between the two universities, student exchange programme exists now.
He also cooperated with NARUSE Jinzō who established Japan women's University to educate women.
Though he opposed SAIGŌ Takamori, he appreciated his human feelings.
In this series, he is described as one of the officials from Saga. He and ETŌ Shinpei who is from the same domain work well under SAIGŌ Takamori. However Shinpei resigns his position after the return of the Iwakura Mission, especially ŌKUBO Toshimichi while he remains behind and continues governing Japan.
(*) At that time, Japan was allied with Britain (Anglo-Japanese Alliance).
The image shows Hiroyuki Onoue as Ōkuma Shigenobu
(From the official website of "Segodon")