Japan spent a lot of yen during their financial crisis of the 90’s – they might be doing it again. The Japanese ecomony is heavily dependent on exports, so they feel it necessary to keep JPY low at (almost) all costs. The very low interest rate is also part of this policy.

Tokyo has let off verbal volleys against sharp yen rises, but so far Japanese officials have stopped short of saying they will intervene in currency markets, and many market players don’t believe they will.

In the early noughties, Japan kept their economic recovery going by selling yen to the tune of 35 trillion yen (US$383 billion). There’s more info here