The plot involved the young "demon spies" trying to find a cache of firearms on the estate of a daimyo before he can use them to rebel against the Shogun, and there were plentiful plot twists and turns before the climactic showdown. [Possible spoiler alert]

One thing that slightly puzzled me is that the lead character says at the end of the film that he wanted to know why his fallen comrades defiantly clenched their fists at their moment of death...what were they grasping for.

Well, I recall earlier in the movie, after the demon spies completed the training their ruthless master vowed to show them one last lesson, and that was how to die properly. So the masked master sliced off his face and killed herself, and clenched his fist as he expired.

So...I guess the students were merely emulating him, but the ending suggests there's some hidden meaning that the surviving hero has to find in his next adventure. I don't believe they ever made a sequel however, so while the ending was slightly ambiguous by intent, the overall the film was very exciting.