In some ways this might show the steady state of a developed economy. Other developed nations are growing in large part through immigration - if the whole world was developed and there was nowhere for immigrants to come from, it's not implausible that we would see something like this start to happen everywhere.

I hadn't thought about this much, but this is an excellent point. I imagine the only thing that would change this in the future is if we made child bearing and rearing a lot less burdensome than what it is right now.... but that seems like a pipe dream, even as I write it down. I imagine economics are only one part of the difficulty with having children; the emotional consequences are probably much more significant.

I don't know why you're being downvoted. The anti-immigration stance is a well known problem in Japan, relaxing it in a sane way would definitely solve some of their social services problems.

Is it being a "well know problem" how Japanese perceive it or how foreigners want them to think of it?

The downvotes are coming from people who think the West is racist and xenophobic and anything contrary to that narrative means downvotes. The fact of the matter is that the vast majority of the world exhibits some form of racism and in many countries, such as Japan, its institutionalize. The U.S. And U.K. get a bad rap on this issue for some reason, but take a few million migrants from all over the world and plop them into Tokyo or Beijing and let me know how it goes.

At least they are not waving flags to welcome radical conservatives escaping theire messed up countrys.