In history, Ōkubo was one of the five Ishin Shishi - Men of Spirit and the last of the three to have the highest honors in the government. He outlived Katsura Kogorō and Saigō Takamori. He was a leader of the Satsuma clan, who supported the restoration of imperial power. He was responsible for the suppression of the Satsuma rebellion in 1877, led by Ōkubo's university friend, Saigō Takamori. In Rurouni Kenshin, Ōkubo appears to Kenshin for help in the Shishio Makoto crisis. In real life, Ōkubo was murdered by six discontented clansmen on his way to Tokyo on May 14, 1878. In the Rurouni Kenshin series, Seta Sōjirō murders him and the clansmen take responsibility.