After a long year, the Bank of Japan unexpectedly finds itself in a sweet spot.

The yen has tumbled in recent weeks, thanks to surging global bond yields, and economic conditions at home and abroad are improving. Though less than bullish, the outlook for the world's third-largest economy looks more promising than it has in years.

"Everything is pointing from headwinds to tailwinds," said Izumi Devalier, Bank of America Merrill Lynch's chief economist for Japan.