This was supposed to be a three stories that tells the events of the Boshin War. In the second story, it was a war front in the Aziu Domain which Jackson's unit received new weapons and uniforms in a deadly struggle for Modern Japan. Meanwhile, Ataru's family and Lum moved to Tokyo that used to be Edo. They faced a struggling challenge under the Imperial rule and Lum's loyalty to her new friends and old friends. This was a context that represent Japan in terms of Modern vs. Tradition.
The Third story was the end of the story, that The Ezo Republic war front as Jackson's unit has ordered one last mission to end the war. They confronted Johnston's Confederate unit that survived from the Civil War Jackson knew. Johnston and his fellow Confederates fled the scene while the Imperial forces won the war. When Ataru was discharged from service along with Jackson was told by Lum's letters to go back to Tokyo.
That's where the climax when Jackson vs. Johnston occurred that it is revealed that Jackson had murdered Johnston's sister. But Jackson offered the truth that he didn't murder her that fallen to deaf ears. During the struggle, one of the soldiers who was Ataru's friend was revealed to be Johnston's spy.
Then I will have explain this: Jackson wins the fight. But soon the falling action goes there which I have a twist in the end that Lum explains Ataru that she must have to leave from this planet that the people of Japan no longer believes in fairy tales no more and thus they have to leave. This left Ataru heartbroken, but she claims they will meet again in another life.
That's all I have to say in this story. I know it's short, but explaining the whole story has got me derailed. So, comment it away of the story.