The article is somewhat schizophrenic. It starts off talking about the shrinking of Japan's labour supply (number of working age people), which is about to apply to the rest of the developed world and China.

But it then goes on to talk about headline numbers (Japan's total GDP growth) rather than adjusting those numbers for labour supply. When you do adjust for labour supply, Japan's performance is average.

It also talks about fiscal and monetary actions taken by Japan's government and central bank, without linking those in any coherent way to the other things.