An upper-class samurai of Tosa Domain, also known by the pen name Zuizan. He was a Bakumatsu idealist who founded the Tosa Loyalist Party and led the pro-emperor expulsion movement in Tosa. In 1861 he organized the party, drawing in members including Sakamoto Ryoma and Okada Izo. By arranging the assassination of senior councilor Yoshida Toyo, he temporarily seized control of domain politics, but was imprisoned under the suppression of domain lord Yamauchi Yodo. He maintained his convictions even behind bars, and in 1865 was ordered to commit seppuku. As a mark of samurai honor he performed the grueling "three-cut seppuku" (cutting the abdomen three times) and died at 36. His dramatic death continues to be recounted to this day. As close ally of Sakamoto Ryoma and master of Okada Izo, he stands as the quintessential Tosa loyalist of the Bakumatsu era.

A man of talent in both scholarship and swordsmanship. He led the Tosa loyalist movement with firm conviction and strong organizational skill, but his intense idealism was ultimately overwhelmed by the rough currents of practical politics. He maintained samurai pride to the very end.

The founding of the Tosa Loyalist Party and his dramatic death embody both the ideals and the tragedy of the loyalist movement. His relationships with Sakamoto Ryoma and Okada Izo are staples of Bakumatsu drama, depicted in countless novels and television series.