Japan doesn’t have Obama.
Mark Steyn deals with this in his book “America Alone.” The problem in Asia is that the birth rate in Korea, Japan, China and even in India is close to 1.3 - 1.5 which is population suicide level. Japanese elders tend to be extremely healthy and they actually have robots for these people to care for them so that they don’t develop dementia. One of the largest problems in Asia (and now being imported to the US) is the suicide of the young. The US had a birth rate above 2.0 when Steyn wrote his book, but it has now fallen; not even the large families of immigrants is able to keep US growth above 2.1.
Japan may wish to go this route, but where will their military arise? They have a very severe policy on immigrants, and even those who stay for many years are not accepted as native.
That describes our society as much as Japan's, unfortunately.
Japan has made two recent advances that may save it.
1. Methane hydrate - lots of it off the coast of Japan, hydrocarbons merged with ice. Unlike oil, no one has yet exploited it. Japan has discovered how to get it to the surface and burn it in a controlled manner. This could be as big as the discovery of oil - and a boon to even the U.S., because we have methane hydrate in the Gulf of Mexico in volumes that rival our original oil supply. Japan helps its economy by producing energy locally instead of importing oil, while certainly exporting the technology they develop the extract methane hydrate.
2. Rare earth metals from sea mud - China is maintaining its export rate of manufactured electronics by preventing the export of rare earth minerals needed to make electronics like smart phones and CPUs. Japan has discovered sources of rare earth metals in mud off their shore, that they can process. Now they get a cheap source for domestic manufacturing. And export.