Highest for USD/JPY since February of 2016
The (specific) pop above 121 was a thin-market stop loss move, but the upwards direction has been persistent ever since the market has dialled back its 'safe haven' buying of yen. Monetary policy divergence between an uber-dovish BOJ and the less dovish (some would even say hawkish) Federal Reserve is a key driver.
Long term chart, monthly candles:
