A skilled carpenter and sculptor named Jingoro is betrayed by his own disciples during the rebuilding of Edo Castle, and a staged accident costs him his right arm and his father. Decades later, he pursues revenge with a prosthetic arm built as a weapon and a partner known as Sleeping Cat. People have taken to calling him Hidari, the Japanese word for left. As he cuts down the men who wronged him, he learns that the Tokugawa Shogunate was behind the plot. His search for the truth brings him up against an army of mechanical soldiers, and before he can face the mastermind he has to save Edo from the castle itself, now turned into a colossal weapon. The movie is an action story of vengeance set in the Edo period.