Nationalist population approaches
Politicians in many countries adopt a nationalist approach towards
present and projected population decline: they exaggerate how
difficult it will be to cope with a decrease, and presume that the
solution is to persuade young people to have more children.
They don't recognize the future danger of a larger (or even
unchanged) population, and disregard immigration as a way of reducing
future decrease.
It is true that Japanese culture is very unfriendly to immigrants,
but the state could do things to reduce that and help immigrants
surmount the obstacle.