Why and How does Algren not face any punishment from either government in The Last Samurai?

Question

At the end of The Last Samurai, after the final battle, we later see Algren with the emperor and other government officials discussing the death of Katsumoto. He is not dead because he survived the battlefield AND did not commit seppeku. Despite changing sides, we see that he is alright and even in uniform.

What bothers me is that he is just free to go, not facing a consequence from neither the American government nor the Japanese government. From their perspective, he is technically a war criminal because:

• He turned on his original side and committed clear treason(the obvious)
• He helped lead the opposing side, he was at the final talks, and he did not wear a helmet, so they can identify him.
• He kills Bagley. Bagley was not a good person, but from the government's perspective, Algren killed a fellow officer, and especially a high-ranking one.
• He can be seen killing many soldiers whose' side he is supposed to be on.
• He betrayed two governments at once technically

At this point, he is not executed, imprisoned, or faces any legal consequence from neither the United States nor Japan. How was he able to walk out of this whole problem?

Note: I know the british guy says he does not know what happened to Algren afterwards, but they show and imply that he just went back to the village.

Answer 1

The inspiration for Algren's character was Jules Brunet, a French military officer and artillery instructor. In reality, it was the French who had been contacted to give military instruction to the Japanese in 1867. Apparently inspired by the Shogun, he switched sides after the Battle of Toba–Fushimi and escaped with another French military instructor and the Shogun's Admiral, Enomoto Takeaki, to what is now Tokyo. It was likely at this point that Brunet first met Saigō Takamori, who was the inspiration for Katsumoto.

After the Boshin War, Brunet was eventually found and arrested. It was requested by the Japanese government that he be punished for helping the Shogun, but he was seen as a hero in France and so that request was denied. He was, however, given a light sentence in France (he was suspended from the Army for 6 months) for his role in the war.

Since Algren's character was based on Brunet, it stands to reason that Algren was allowed to walk away without punishment.