During his first fight with Hanzou, Jiro sustains a wound on the left side of his midsection. As he is resting at a hot spring area, he is tending to the right side of his midsection.
Mark Twain was the pen-name of Samuel Clemens. In the movie, however, he meets Jiro and identifies himself as Mark Twain. Samuel Clemens never referred to himself by his pen-name in real life.
During the title shot, the title of the movie is shown first in English, and then in Japanese calligraphy. In the English title, the word "dagger" is misspelled as "daggar".