Sacrifice & redemption
When I watch a good movie, I always seem to struggle to put to words how I felt about it. With most good movies, it is the case that you get can get different meanings out of it, with each viewing. I believe that to be the case with The Last Samurai.
For me, sacrifice & redemption seemed to me to be the key theme of this story. From the main character, making peace with his past and choosing to sacrifice his former persona in order to take up the way of the samurai, to the emperor choosing to sacrifice his relationship with his right hand man in order to save the Japan from a potentially frightful peace treaty, simutaniously redeeming his dignity, which was lost.
Yes it can be a little on the nose with its religious undertones, but that is all overshadowed by its great character work and writing.
Capt. Nathan Algren (Tom Cruise) is an American military officer hired by the Emperor of Japan to train the country's first army in the art of modern warfare. As the government attempts to eradicate the ancient Samurai warrior class in preparation for more Westernized and trade-friendly policies, Algren finds himself unexpectedly affected by his encounters with the Samurai, which places him at the center of a struggle between two eras and two worlds.