A rural samurai of Tosa Domain and member of Takechi Hanpeita's Tosa Loyalist Party, he was one of the most feared assassins of the Bakumatsu era, carrying out numerous killings under the banner of divine retribution. An outstanding swordsman, he cut down opponents of the loyalist cause and pro-shogunate figures in Kyoto at his master Takechi's direction. When the Tosa Loyalist Party was suppressed amid internal power struggles, he was imprisoned and, unable to withstand torture, confessed the names of his comrades one by one—contributing to the party's destruction. He was beheaded in 1865 at age 27. He is widely known in modern times through Shiba Ryotaro's short story "Hitokiri Izo."

A tragic assassin of first-rate sword skill but lacking political wisdom and inner strength. Torn between loyalty to his master Takechi and his own weakness, his confession under torture inspires a complicated pity.

Widely known today as the subject of Shiba Ryotaro's "Hitokiri Izo." His portrait combining sword talent with human frailty embodies the tragic dimension of the Bakumatsu era.