It is far too early to declare, "that Japan is back." Japan's challenges are legion -- a shrinking population, natural disasters, soaring debt, a high cost structure that inhibits competitiveness, and most of all deflation.
The reason for this is clear; Japan's debt has ballooned to over $12 trillion and is now 237% of their GDP. So, what's a government and central bank to do? The answer of course is enacting yet another new fiscal stimulus package that will be monetized by the BOJ.