Accurate representation of Ninjas in film?

Ninjas did exist. They were some sort of the anti-thesis to the samurai and did not adhere to the Bushido code of honor....which is among the reasons why they wore masks and carried a "regular" sword. I think they did not serve a particular lord (perhaps secretly, as assassins). I think they were depicted in the movie "The Last Samurai" though it was just a scene there. I don't think there would be a "serious" film that would accurately depict a ninja because of its obscurity and being "secretive" of their society. Ironically, its obscurity and being secretive propelled them to such a mythical status in pop culture. I would say that it wasn't a good idea way back then to admit/proclaim one's self as a ninja. That would be a contradiction. Also, owing to the nature of their function/status, no one in his right mind would trust a ninja, as such person (ninja) would be unworthy of trust and honor. I myself would be interested if there indeed is a movie that accurately depicts these "shadow" warriors. Good luck, though.