Machibuse (Ambush) (1970)

In the Edo period, a nameless ronin accepts an assignment to go to a mountain pass and wait. Near the pass he stops at an inn where a collection of characters gather, including a gang set on stealing shogunate gold that's soon to come over the pass. When the Ronin's assignment becomes clear, to help the gang, he's ordered to kill the inn's residents, including a woman he's rescued from an abusive husband. He's reluctant to murder innocent people; then he learns that the gold shipment is a trap and he's part of a double cross. How he sorts through these divided loyalties tests of his samurai honor, and perhaps of his love for a woman.