This is one fun movie, and just like the trailer it's full of ninja, fights and explosions, not to mention a fair amount of magic and blood. Sometimes these all occur at once! The movie is a bit episodic, since it's based on a comic book and assumes some familiarity with the characters.
I would have loved this as a kid though, even with no giant monsters. Watari proved to be a hit and Toei made a few Red Shadow compilation movies into "Watari" movies, several dubbed into English.