Short answers, pulled from the story.
The Empire of Japan committed numerous war crimes including sexual slavery, massacres, unethical human experimentation, torture, starvation, and forced labour. These acts resulted in millions of deaths across Asian and Pacific nations from 1937 to 1945.
Japan signed the 1929 Geneva Convention on the Prisoners of War but declined to ratify it fully. The government stated in 1942 that it would abide by terms mutatis mutandis while violating other international agreements like the Hague Conventions of 1899 and 1907.
Unit 731 under Shirō Ishii conducted experiments on civilians and prisoners of war to develop biological weapons. Victims were subjected to vivisection without anesthesia and exposure to plague germs between 1937 and 1945.
The Memorial Hall of Victims of the Nanjing Massacre inscribed a death figure of 300,000 at its entrance in the early 1980s after conducting extensive interviews with survivors. International Military Tribunal Far East findings state the Japanese Army massacred as many as 260,000 civilians and prisoners during 1937 and 1938.
Operation Cherry Blossoms Night was planned to launch on the 22nd of September 1945 but Japan surrendered five weeks earlier on August 15. The plan involved using plague weapons against U.S. civilians in San Diego to spread terror.