I once read that about 1/3 of American POWs died in Japanese captivity, while only about 3% captured by the Germans did. As shown by this article, the Japs had no regard at all for international agreements like the Geneva Convention. I have to wonder if there isn't some correlation with the fact that Japan has been more resistant to the spread of Christianity than almost any other country outside the Islamic world. Christianity still had some hold over many individual Germans.
The numbers that you cite are correct, not just for Americans but for the British and Australians as well. Interestingly enough, apparently the Dutch colonial POWs of the Japanese suffered only? a 20% mortality, attributed to their better knowledge and practice of tropical medicine. My generation,I was a child during WW II, still thinks of them as JAPS, now a pejoritive term
FYI, a greater percentage of Americans in Chinese captivity died during the Korean War than did GI's captured by the Japanese during WWII. A sobering statistic.
Many Japanese Christians (there have been Christians in Japan for around half a millennium) were crucified during World War 2 by their own government--and were persecuted for a long time before that.
To me, the Japanese are a riddle wrapped in an enigma. And anyone who thinks Japanese society is stable is kidding himself. Their society used to rest on Shintoism. Now it rests on nothing but consumerism, and that's a very slender reed.