Ōkubo Toshimichi (大久保 利通) was a legendary Ishin Shishi leader and samurai from Satsuma who became a major official in the Meiji Government after the end of the bakumatsu, taking the seat of Chief of the Department of Internal Affairs. On May 14th of 1878, Ōkubo was murdered by the Juppongatana's Seta Sōjirō after enlisting the help of Himura Kenshin against the Juppongatana's leader, Shishio Makoto.
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.