1. Teacher Jiang once witnessed the conversation between Carcaba and the German old man. Kakukawa was worried that Teacher Jiang might expose his crime or threaten him with it, so Kakukawa chose to kill Teacher Jiang to protect himself.

2. More importantly, Kakukawa is a Japanese with human nature, and he has some understanding and reflection on the Japanese atrocities in Nanjing. He knew that if Mr. Jiang was taken to the comfort station, he would definitely be humiliated by the Japanese, and his life would be worse than death. For a neat woman, this loss of dignity may be more painful than death. Therefore, Kakukawa chose to kill Teacher Jiang out of respect and protection.

It should be noted that the above reasons are all the plot settings in the film, which are not necessarily the true reflection of real historical events. In specific historical events, Japanese atrocities are undeniable, but specific to individual behavior and motivation, more specific historical evidence may be needed for research and discussion.