Ogami Itto is the Shogun's executioner, the Kogi Kaishakunin, a lofty position in feudal Japan. Itto's rival, Yagyu Retsudo, kills Itto's wife and handmaidens and frames Itto to make it look like he wants to kill his Shogun, leaving Itto's 1-year-old son, Daigoro alive. Itto sets off with his son to live as 'demons' or assassins for hire until he can find and reap his vengeance upon his mortal enemy, Retsudo and the entire Yagyu clan.