Zankuro Matsudaira (Ken Watanabe) is a low-grade vassal of the Tokugawa Shogun, forced to moonlight as a bodyguard and executioner to make ends meet. He also has a drinking problem, an overeating mother, and a propensity to protect the oppressed, all of which eat into his finances. His confident mother Masajo (Kyoko Kishida) is the descendant of a famous family of shogunate retainers and a mistress of the pen and sword, who regards her son as a failure.
