One thing Japan and Germany had in common was their medical experimentations on prisoners throughout the war. They did different tests, but they shared a common conclusion; almost all of their patients died. The experiments ranged from testing gases to finding human boundaries of survival.
One doctor in particular was oversaw many of the experiments on humans. His name was Eduard Wirths and he supervised the experiments done in Auschwitz. His specialty was twins. He did many experiments on twins, including sowing them together to form man-made Siamese twins to see what would happen. He committed suicide after he was captured in 1945 by British troops.
One other doctor of a concentration camp, Sigmund Rascher, specialized in cold temperature experiments. Victims were placed in tubs of freezing cold water to discover the limits of the human body. He tested about 400 subjects with experimental life vests in cold water. In almost all of his studies, the victim succumbed to hypothermia and died.
Other medical experiments consisted of mass sterilization, exposure to extreme temperatures, transplants, head injury experiments, burning, altitude limits on human body, and countless other sadistic experiments.
Although the Japanese claimed they were doing experiments, in reality, they were really finding more creative ways to kill their prisoners. One unit in particular focused and specialized in biological warfare and experimentation. Unit 731 disguised themselves as a water purification unit and committed several experiments on Chinese and Russian prisoners. The unit was based in a huge compound and over 9,000 people died from their testing. Over 10,000 are killed in the field from toxins and diseases. At the end of the war, the compound was destroyed and Unit 731 was disbanded in a Japanese attempt to cover up tracks.