All this chatter about a so-called global currency war is utter nonsense.
All that is happening is the Japanese are wisely taking steps to increase liquidity and depreciate their vastly overpriced yen. They are doing this in order to avoid deeper and deeper deflation. That deflation will sink the Japanese economy for years to come if remedial actions are not taken.
Among all the big economies, none needs quantitative easing more than Japan's. All the Japanese have done so far is make cheap loans to banks, but with no concerted quantitative easing. But QE is coming this spring, when Prime Minster Abe appoints a new Bank of Japan head man.