It was just a matter of time until the Yen dropped back to pre-earthquake levels:
The above is the U.S. dollar rising against the Yen.
The Bank of Japan will intervene again at some point, but this may still have legs to go.
Here are straddles on FXY for April and May, which allow profit regardless of direction, as long as the stock moves ther necessary amount.
Note: Please do your own due diligence. This is not advice. Options are very dangerous and may cause 100% loss. Computed with StraddlesCalc Tool