Make no mistake about this film. It is grim and ghastly and I am not only talking about the transfer to DVD and the dubbing. All the characters talk with an inexplicable mock english accent, all vaguely similar, complete with the phrasing, delivery, and accentuation, but minus the farting noises, to Terrance and Philip's on Southpark. You will want to look away more than a few dozen times.
What occured at Unit 731 matches or exceeds anything doled out in shovelfuls and the boatload during the WWII conflict and I suspect any other conflict, you wish to name. Then it all ended, and those in command of Unit 731, for the most part 'walked', much like some of the Germans, with their own newfound value, did too... thanks to the gobal cooling of the developing Cold War. Their crimes buried away somewhere, for the good of the national interests.
see http://www.ww2pacific.com/unit731.html and other sources on the Web and elsewhere for more information about this fun factory. As much as you may care not to believe it so, Men behind the Sun may just as well have been a documentary. I doubt whether the circumstances could have been protrayed with any more horror than you will see here.
WARNING! there are some extremely gruesome scenes..