Harakiri aka Seppuku (1962) dir. Masaki Kobayashi
Post-War Japan was a period of intense adjustment, as the society reacted both to the sudden influence of American culture and the horrors of Imperial Japan. In Late Spring, Ozu found a way to move Japan into the new world while still honoring traditional values. Kobayashi's later film, Harakiai, on the other hand, cannot see a way to reconcile the two.
By 1962, the tropes of Samurai films were well set. They largely portrayed the Samurai as spiritual warriors, fighting under an ancient code that ennobled their violence. The themes were analogous to the stories of chivalry among western knights. They would often be set in the 19th Century, to better contrast the Bushidō with modern warfare.
Japanese filmmakers and writers could use the idea of Bushidō to delegitimize the war criminals of the Imperial system. If people believed that true Japanese values taught one to respect one's enemies and put the law above personal gain, people would see the new democratic system as a natural fit for Japan, and accept it more readily. Consider Sansho the Bailiff as an example.
But there is something in the standard samurai film script that is still unsettling. The mourning for bygone days of honorable violence seems reminiscent of the "Moonlight & Magnolias" tropes of the antebellum South. (Especially when you remember who the enemy of both Imperial Japan and the Confederacy was, and how that enemy won.) And endorsing honorable violence is still endorsing violence.
Kobayashi's Harakiri seeks to deconstruct the idea of Bushidō. Harakiri is set in 1630, near the beginning of the Edo Period and the romantic heart of the Bushidō Code. Here, the samurai are not noble mystics, but spoiled elites who do not fight and care nothing for their unemployed former comrades. When the starving ronin come knocking at the door, the samurai's primary concern is how to make them go away. Although they use Bushidō as an excuse, their hypocrisy is exposed easily.
"The thing we call samurai honor is nothing but a facade," our hero tells those using Bushidō to keep him captive. He defeats their strongest warriors, and traps the clan's leader into creating a dishonorable cover-up. And in full view, he reveals the family's revered suit of armor as a hollow shell.
Kobayashi doesn't give into the temptation to take a next step and offer his own code as a replacement. There aren't any Marxist screeds or other leftist hints thrown in that are common in other anti-establishment films from the same time period. 50+ years later, these often seem dated, and serve to mute a movie's impact. Harakiri makes a simple, direct plea to common humanity that cannot go out of date. Do not let a 'code' or an ideology serve as an excuse to help those in need.