Director Tun-Fei Mou paid a lot of attention to the film's historical accuracy and sought to create something that very earnestly captured his true-life source material doing years of research. He chose actors who purposely resembled Japanese people of the war era and even cast Korean kids living in China to play the Youth Corp as Mou thought Koreans most resembled Japanese kids of that era. Mou filmed the movie in Harbin, Manchuria where 731 was stationed. He used 731's real headquarters as a location, it was a school at the time of the shoot. When Mou took down the school's name and put the Japanese flag back, it horrified the local elderly who had lived through the war. One particularly upset old lady approached Mou and his crew and said "I knew they'd be back (the Japanese), I just hoped it wouldn't be this soon!"

Film