At first watch, this film is more comedic and less compelling than Yojimbo. At its essence, this is a buddy flick, but Sanjuro has a double handful of impetuous idiots to wrangle instead of just one. Because of this, Sanjuro’s utmost capability stands out at all times. He comes across as an ubermensch ronin who’s so bored with being a badass that he helps out these bumblers just to enliven his day. This might actually turn the film from a comedy into a satire.
I would make the argument that there is an implicit critique of Japanese social structure here, all the mundane samurai are the medieval equivalent of modern salarymen and they all want to be like the bossman, Sanjuro. He, on the other hand, is self-priming and autonomous. Because of this, he is filled with a kind of whimsical contempt toward the other samurai who place worth on things external to themselves. This is a lonely place for Sanjuro, and would irrevocably darken the tone of the film if not for the presence of Mutsuta’s wife. She’s the only other non-villainous character who has the same sort of self-possession, and her peace with herself is a marked contrast to Sanjuro’s discontent. He recognizes this, and the refinement of her personality gives Sanjuro a foundation from which he can launch his fury.
The recipient of this ire, and the only other character Sanjuro instinctively respects, is the other autonomous actor: Hanbei Muroto. Though forced to kill him, Sanjuro has no desire to do so, and the film ends as he continues his search for a group of his equals.