Isn't it going to hit all western countries hard? Seems to me Japan is just first in the list...
As far I'm concerned, I'm living in Europe and I'm not confident at all that I'll get any retirement before my 70. Knowing that the lifespan increased a lot but not necessary the good-shape-span, it seems to me a better strategy is to enjoy more free time now by reducing work hours than to bet on an uncertain future.