존왕양이
Shimazu Nariakira recognized Ōkubo's talents and appointed him to the position of tax administrator in 1858. When Nariakira died that year, Ōkubo joined the plot to overthrow the Tokugawa shogunate, the "de facto" military dictatorship that had ruled Japan as a feudal state since 1600. Unlike most Satsuma leaders, Ōkubo favored the position of "tōbaku" (倒幕, overthrowing the shogunate), as opposed to "kōbu gattai" (, marital unity of the Imperial and Tokugawa families) and "hanbaku" (opposition to the shogunate) over the "Sonnō jōi" movement.