Four Hitokiri of the Bakumatsu

The Four Hitokiri of the Bakumatsu (幕末四大人斬り, Bakumatsu Shidai Hitokiri?) was a term given to four samurai during the Bakumatsu era in Japanese history. The four men were Kawakami Gensai, Kirino Toshiaki (also known as Nakamura Hanjirō), Tanaka Shinbei, and Okada Izō. They opposed the Tokugawa shogunate (and later, supported the Meiji Emperor). These four samurai were warrior elite and widely considered undefeatable by normal people. The word hitokiri literally means "man slayer."
Along with the title of hitokiri, the four men were also referred to as "The Four Butchers" or "Heaven's Revenge against the enemies of Imperial restoration". Most of them came from the Chōshū-Satsuma domains, which were largely anti-shogunate at the time.