There appear to be two major factors for the Yen's freefall. The first factor is the positive U.S. economic data, and the second factor is the rise in most of the Asian Stocks. The combination of the two is leading investors to look for riskier assets than the Yen, as risk-appetite increases following the recovery of two of the largest economies. It currently seems that as long as the U.S. and the Japanese economies will continue to report positive data, the Yen might weaken further.
As for this week, a batch of data is expected from the Japanese economy. However the most significant publication looks to be the Overnight Call Rate on Friday. The Overnight Call Rate is the Japanese Interest Rates announcement for May. Analysts have forecasted that the Bank of Japan (BoJ) will leave rates at 0.10%. Nevertheless, if the BoJ will surprise and decides to hike rates, the Yen is likely to be boosted as a result.