Specifically the ones that had been held by allied powers (not nationalist China). It looks like most were held in camps in Australia, New Zealand, and America. How were they treated when they were returned to Japan?
Japan's military culture had been thoroughly defeated by the allies. Only 22 of the armies 1500 generals killed themselves due to the shame of defeat, and only about 600 officers killed themselves in total. Given the total defeat of Japan, it is actually a rather surprising number. It also meant any sort of mass reprisal against "perceived cowards" was out of the question. Japanese officials tried to prevent mass humiliation by changing the wording of their order asking for all Japanese personnel to lay down their arms. Their change stated that all those who surrendered would not be considered POWs as they were doing their duty. Now that meant that those Japanese soldiers were treated normally.
The real question is what happened to those who surrendered before. They were treated well by society. The Army had always been responsible for propaganda and enforcing the idea that surrendering was "shameful". Most Japanese POWs were not sent back to Japan until a few years after the war, the ones captured by the Soviets, even longer. After the destruction caused by the mass bombings, people wanted to see their loved ones and return to a normal life. However, soldiers who suffered from shell shock were not cared for, and were in fact stigmatized. There was also no safety net or really any veteran organization. So the Japanese soldiers found themselves isolated and unable to reintegrate into society; and there was very little in terms of aid that these people could receive
Now the officers, that was a different story. The Japanese people and ex soldiers began to lash out against their officers, they had made them fight in impossible situations, made them live in inhumane conditions, the officers who had brutalized them and commanded through fear, rather than respect. In May of 1946 a veteran wrote a letter to a very popular newspaper in which he talked about the abuse and starvation he had endured at the hands of the officer corps. There were reports of soldiers lynching their former officers.
Sources:
Japan's Imperial Army Edward Drea
Embracing Defeat John Dower
Also could someone confirm that Japanese were actually held in New Zealand POW camps I don't remember ever hearing or reading anything about POW camps here it seems that it would be a long way to take them as there was never conflict on NZ soil during the war.