The Japanese government has been aggressively devaluing the Yen, because they're bankrupt and can no longer afford to pay even the interest on their debt without either using printing or new debt issuance. They're stuck in a downward spiral. Japanese savings have collapsed to zero, so the Japanese people can no longer afford to fund continued government debt expansion as they were before. That has left the Japanese government with no other options but currency debasement, ie devaluing the real worth of outstanding Yen based debt (which is mostly held by Japanese citizens, which is then ultimately a slashing of their wealth).
Japan has suffered zero deflation over the last 25 years. That's why Japan is one of the most expensive places on earth to live in most every respect. If they had suffered 25 years of deflation, their prices would have gone down accordingly.
Their long-term price index shows zero deflation.
http://i.imgur.com/Cvwj26A.png
The notion they've been stuck in deflation is keynesian economists confusing what deflation is. Under keynesian economics, if a bubble is inflated, and then bursts, taking down real estate prices, they call those falling prices deflation - when in fact it is not. This is one of the many obvious flaws at the heart of keynesian economics, which has helped lead the globe into its current perpetual stimulus addiction path.
It is the dollar that has appreciated, not the yen that has depreciated. The dollar has appreciated against most currencies in the last year – probably because people expect interest rate hikes this year. It has nothing to do with Japan per se.
If you have to significantly harm your currency to get growth, what you're getting is not actual growth, merely an illusion.