Lone Wolf and Cub: Baby Cart in the Land of Demons (1973) on Netflix

Plot summary

Ogami Itto travels the Demon Path with his young son, Daigoro, hiring out his sword. Five messengers from one clan come at him in turn, each testing his skill; beaten, each hands over part of his fee and part of the reason for the killing. They describe a conspiracy: a daimyō's illegitimate daughter is being passed off as the clan's heir and prince, while the true son is held hidden and imprisoned. A letter spelling out the plot is on its way to the shogun in the hands of a high priest who is in truth a secret agent. Ogami must take the letter and kill the carrier, who travels under the guard of his old enemy Yagyū Retsudō. At a festival, Daigoro is separated from his father and falls in with Oyo, a pickpocket wanted by the militia.