Men Behind the Sun (, literally Black Sun: 731, also sometimes called Man Behind the Sun) is a 1988 Hong Kong historical exploitation horror film directed by T. F. Mou, and written by Mei Liu, Wen Yuan Mou and Dun Jing Teng. The film is a graphic depiction of the war atrocities committed by the Japanese at Unit 731, the secret biological weapons experimentation unit of the Imperial Japanese Army during World War II. It details the various cruel medical experiments Unit 731 inflicted upon Chinese and Siberian prisoners towards the end of the war. It is the first film to be classified "level III" (equivalent to the US rating NC-17) in Hong Kong. Plot The film opens with the passage "Friendship is friendship; history is history." A group of Japanese boys are conscripted into the Youth Corps. They are assigned to the Kwantung Army, and are brought to one of the facilities serving Unit 731, which is headed by Shiro Ishii. Soon, they are introduced to the experiments going on at the facility, for which they feel revulsion. The purpose of the experiments is to find a highly contagious strain of bubonic plague, to be used as a last-ditch weapon against the Chinese population. Meanwhile, the young soldiers befriend a local mute Chinese boy with whom they play games of catch. One day, the commanding officers ask the boys to bring the Chinese child to the facility. Naively, they follow orders believing that no real harm will come to the boy; however, the senior medical staff places the boy in surgery for the purpose of harvesting his organs for research. When the young soldiers realize what has happened, they stage a minor uprising by ganging up and physically beating their commanding officer. As the war goes on, the situation becomes increasingly desperate for the Japanese, and therefore Unit 731. In one of their last experiments, they tie a number of Chinese prisoners to crosses, intending them to be used as targets for a prototype ceramic bomb containing infectious fleas; however, they are not able to contact their airfield due to a retreat. Chinese prisoners break free from the crosses, and attempt to escape; however, Japanese troops hunt them down, and nearly all of them are run over or shot, including several Japanese. Returning to the facility after the aborted experiment, Unit 731 runs out of time and they are