Japanese troops round up Chinese and Russian prisoners of war and take them to unit 731, where they're horribly tortured and experimented on to test new biological weapons.

During the shut down and destruction of the Japanese test camp Squadron 731 in Manchuria, a soldier becomes infected with a virus developed during the camp's testing and risks spreading it into Japan on the train ride home.

Black Sun: The Nanking Massacre depicts the brutal events behind the Nanking Massacre committed by the Imperial Japanese army against the Chinese people during the Second Sino-Japanese War.