Just a thought.
No matter how depraved the movie is we will never be able to understand or comprehend the horror of Unit 731. The reality is that what they did was so repulsive, no movie, not Men Behind the Sun or Philosophy of a knife can do real justice to how evil it really was.
Put yourself in their mindset for a second. Imagine being 8 years old, with no supervision and believing in your heart that your job, your sword duty and obligation was to experiment on fire ants to better understand them for the protection of your family. Then imagine all the tools you could ever dream of at your disposal, a hammer, firecrackers, a lighter, glue, hairspray, bleach, box cutter, etc...
Now transfer that entire mentality on to the Japanese that were there. We were the ants, and they had the tools and the belief that their work was important.
Whatever, just a thought.