Sword of the Stranger is set during the Sengoku era in Japan. Chinese warriors are chasing Kotarou because only his blood can make the Chinese Emperor immortal. That is the plot of Sword of the Stranger. It's not unique, but it doesn't have to be. It's good enough as it is.
The animation is superb. The fighting is not lazily animated, and every named character's movements are unique. The are some of the best animated fights that I have ever seen.
The music is also good. Composed by Naoki Saito, the music accompanies the scenes beautifully. The main theme is played in various forms to produce different moods throughout the film. The final 30 minutes of the film is especially powerful because of the music.
There will probably only be two characters that you will care about: Nanashi and Kotarou. A lot of the film follows their interaction with each other, and you will care about them. They form a beautiful bond that lasts from the beginning to the end. The other characters are static, but that is not so bad. The movie knows who the important characters are.
My favorite scene occurs early in the movie. When Kotarou returns from stealing some fish (to an abandoned temple), he sees a man laying on what seems to be the altar. That one still scene is awe-inspiring. Nanashi is resting with his hands behind his back and the head of a Buddha statue is in the background, reinforcing Nanashi's image. And the music, what music! The scene would not have been as powerful without the music. With scenes like this, it is no wonder that Sword of the Stranger is my favorite anime.
Character Analysis : Part1 Part2