Japan was supposed to obey the law during the second world war. However, the Nanjing Massacre still happened. Hirohito, the Japanese emperor, deliberately avoided mentioning the International Treaties in the imperial rescript of the Great East Asia War in 1937. The Nanking Massacre was carried out according to the Japanese army’s interpretation of the imperial rescript. Such a legal interpretation was rooted in the idea that Japan had to educate the Chinese and transform China by killing its people in order to pursue a Greater East Asia Co-Prosperity Sphere led by Japan. In the film Black Sun: The Nanking Massacre (1995), we can see both a justification of and an opposition to killing. In this paper I am going to show how the imperial rescript is used to justify this mass killing is and how opposing arguments are used to show its cruelty and absurdity, which is taken as a means to achieve a greater good.