OK, so speaking only to the issue of Soviet captures, keep in mind that the Red Army only entered the conflict in August, 1945, as had been agreed with the Western Allies. During combat operations, as cited from an August 30th report found in David Glantz's "Soviet Operational and Tactical Combat in Manchuria 1945", "89,831 soldiers, 1,702 officers, 16 generals, and one rear admiral" were captured between the beginning of hostilities on the 9th and the 29th, by which point Japanese resistance was pretty much gone, with the official surrender ceremonies only a few days away. Now obviously that is a lot of prisoners, but it isn't hundreds of thousands. Those hundreds of thousands became prisoners because of the Japanese capitulation, which saw the Soviets overseeing the disarmament and internment of the Japanese forces in their AOE, and would have seen the Chinese, and the Western Allies dealing with similar massive numbers in their areas in need of disarmament. The prisoners taken by the Soviets are of questionable numbers, as noted by Dower in "War Without Mercy".

As of October 1948, the U.S.S.R. had repatriated 877,015 Japanese. The following May, the Soviet government announced that only 95,000 prisoners remained (plus some accused Japanese war criminals), and they were repatriated by November 1949. The Japanese government claimed that 374,041 Japanese remained unaccounted for.

So yeah, that is the sum of it. The Soviets only captured ~100,000 Japanese under combat conditions, and the majority of their prisoners were taken after the Japanese capitulation. The other Allied powers would have taken not dissimilar numbers of prisoners then too, but while I believe they were not interned the same way, that is a topic another flair should maybe speak too, not me.

Okay so there are a ton of factors going into these cases of Japanese soldiers being captured by different countries, in different parts of the world, and at very different times. So I guess I should start first off with the Americans taking prisoners. At the start of the war there were many more attempts to take Japanese prisoners by American soldiers but it was the Japanese themselves that discouraged this. The Japanese soldiers were at this point in time told that to surrender would first off be a death sentence where the Americans would torture them, refuse madical care, and not give them any real amenities once captured (I.E. Beds, housing, bathrooms). Secondly they were told that if they were found to surrender they would dishonor their family name and bring repercussions upon their very families, their parents would be shunned, sisters would never be married, and upon returning home they themselves would be executed. This lead to the Japanese soldiers (who come from a culture where bringing trouble on others you care about is a million times worse than hurting yourself) would choose suscide over harming those back home as well as the torture they were promised at the hands of the Americans. So where injured soldiers would be offered aid by American soldiers they would cling to the men and set off their grenades taking the enemy with them so they don't die in vain. As well a Japanese soldier would be sent out to surrender to Americans and would say his friends would surrender as well leading the men into a trap where his friends would gun down their would be captors. In cases where Japanese soldiers would actually be captured they were often too injured to attempt suscide or were too shell shocked to resist and in these cases it would be only a handful of men from thousands.

As you can imagine after watching their friends get blown apart when trying to capture Japanese soldiers the American soldiers began to shoot on sight rather than risk death for a slim chance that they weren't hiding a grenade. Also there was a thought that the average Japanese soldier wouldn't have any usable information so it was seen as risk with no reward. (Though of course there were still some prisoners taken but they would ususally first be stripped naked as to prove they weren't hiding weapons. So as time went on later in the war people began lobbying for Japanese prisoners to be taken and programs began to re-train soldiers in the usefulness of taking the men alive and breaking the myth that they didn't have any info. At this time as well the war was going worse for the Japanese and their ranks were more and more filled with scared starving young conscripts who were more willing to get out alive than anything since the future was bleak. At this point where both of these factors came into play and you can find a major spike in prisoners taken.