At work so I can't currently answer extensively but their mass return posed a serious problem that the Japanese government, and naturally, the occupying US forces had to deal with.

First, Japan was starving.

The loss of her many colonies meant that there was a sudden shock to the food supply. Korea, for example, was a major source of rice, fruits, vegetables, etc for Imperial Japan. A sudden loss of this major line of food was a terrible strain on the system.

This is on top of the extensive damage the US airforce had already done to the Japanese food distribution and storage network. Even without the additional millions returning, Japan was facing mass starvation and many had already been starving for months before the atomic bombs fell.

Those that weren't starving were already on tight rations of everything from rice, water, cloth, sugar, etc. Just about everything.

Second, Japan was facing massive unemployment.

Lots of hungry, unemployed people who have no way to improve their situations because of the lack of jobs can quickly turn into a murderous mob, as history has shown us time and time again. The added millions of colonialists and soldiers returning would certainly not have jobs lined up and most did not have much in the way of assets.

Even the rich might be returning poor and destitute because they likely had much of their money invested into colonial holdings and developments, which were now all forfeit.

As one can imagine, the millions of returnees exacerbated this problem.

Third, the military was certainly not welcome in many parts.

While it isn't as simple as saying 'everyone hated the military and all those associated', saying that the average Japanese person was war weary is a huge understatement. Many indeed did blame the military for their suffering and loss and even those that weren't angry were certainly feeling lost.

What did they gain from losing millions of young men, who fought and died far from home and family? What did they gain for the families and neighbors that were killed by bombs, fires, rubble?

And of course, particularly in rural areas, few returned at all. Anger that someone else returned and not their loved ones is all too real.

At the very least, the military generally did not receive the warmest of welcomes.

I'll write more later!