Ultimately the problem is that Japanese people are not having enough kids. It's a huge emergency. It is recoverable, but it has to be done very soon or it will be much harder. Right now, 5.1% of the population is 25-29, prime childbearing years. If all of those people had 2.1 kids, and so did their descendants, Japan's population would stabilize reasonably well. The problem is that the 0-4 range is only 3.1%. Even if that generation has 2.1 kids, the population will be massively diminished.
If that happens, the majority of Japanese people will be retired, and the cost to provide medical care for them will be astronomical compared to the number of people that can provide that care. It's easy to say "Japan is a rich country, they can afford it." However, medical care for old people is very labor intensive. Even if the old people have "savings", this is just a claim against the labor of young people. If the young people are too worn out from caring for their parents to have their own kids, the country dies out.
The only solution I can think of is to provide massive incentives to have kids. Massive meaning something like "you get $40k per year for every kid in your house under 18", or "you get a free house when you have your first kid, and a bigger one when you have your second."
Maybe this sounds extreme, but the alternative is that young people are taxed at punitive rates in order to provide care for older people. As the situation progresses, younger people will have even less kids because they can't afford them, and eventually they won't even be able to pay for a reasonable living standard for themselves. Older people won't care and will vote themselves excellent benefits, since they would have a good majority in voting. The only option younger people would have would be to leave the country, which only forces the tax rates higher. Eventually something breaks. It's difficult to predict exactly how it would go but it's not pretty.
If Japan is to be saved though, it has to happen in the next 5-10 years or so, and the sooner the better. Once the population pyramid slides up another decade, you'd need the average couple to have 4 kids or so, and the incentives required to make that happen are not affordable, and wouldn't be agreed to democratically when the majority of the population is retired and wants the money for the remainder of their lives rather than paying for kids that would be too young to provide labor to care for them while they're alive.
> If Japan is to be saved
As I said in another comment, the population of Japan is projected to be 64 million in 2100. A hundred years ago, the population was 64 million, and that was at the peak of their colonial expansion.
Yes I get it that the demographics pyramid would not be the same as it was in 1930, but this whole narrative that "Japan is dying" is at the very least spread to pull on heartstrings in order to fuel this lines must go UP ALL THE TIME hypercapitalist nonsense.
Why can't a people wax and wane according to the needs of their culture and not the needs of bigwig bank accounts? Does Japan need a convenience store on every block? If every single convenience store disappeared tomorrow, you'd suddenly have a massive workforce able to go to school or care for the elderly, so here I am just yelling at clouds while the average Japanese person is more in line with your way of thinking that being able to buy a sandwich instead of making your own is the "Japan" they want to save.
Has any country really reversed the diminishing fertility rate with industrialization without religious zealotry? I honestly don’t think money is the factor here. Yes it matters but $40k is nothing. That covers maybe a year or two of daycare in the states. It needs to be a cultural change but not sure what would reverse it.
Or we set a max age of the population where you off yourself. It’s the plot of Half a Life in Star Trek TNG