The story takes place at the end of the Edo's period (around 1860) in Japan. At this time, Japan was divided in two between patriots who wanted to bring the emperor to the government and shogunate forces who protect the head of state, the Shogun.

A poor samurai, Okada Izo, is hired by the patriots to assassinate shogunate members, the story follows his story.
This manga is based on real facts and was inspired by the movie of the same name.