That is news to me. What is your source?
It may have been a volume specifically on POW treatment by the Japanese but I am uncertain. My own library has grown, shrunk, grown and is now dwindling as I sell things off.
I will check the remaining Pacific theater volumes I have left.
Page 96:
“ The Japanese had regulations about prisoners of war dating from when tey first fought against white men, in the Russo-Japanese War 1904-105. The Japanese won that war. They were concerned at the time to be seen as a people of elevated morality in the modern world, fitted to make 20th century war in a civilized way, up to Western standards.
POWs of the emperor, the Japanese regulations said, were to be treated with a spirit of goodwill, never subjected to cruelty or humiliation, etc. And that is how the Russians were treated “
On page 284 he discusses how the Japanese came up with the rules and sizes of transport for POWs which dates back to, again, the Russo-Japanese War.
I know very little of that war but I suspect the Japanese took a large number of Russian POWs based on how one sided the affair went. That and the fact the Japanese had to figure out how to transport POWs and made regulations in this regard.