BoJ's dovish move to introduce negative rates was in response to poor inflation in Japan and a strengthening JPY; the latter has the potential to cause a negative impact on its economy and its exports. Nonetheless, in the short term, the JPY should weaken on this news.
The pair has made a momentum break above L4 support -119.30 and EMA89 has closed above, suggesting a valid breakout. The price may either a) continue with the trend b) retrace to POC zone (DPP, L3, 50.0). Watch the chart carefully- because we have a strong momentum break on USD/JPY we might see a shallow retracement to 23.6 (blue coloured -121.00) and the price might continue towards H3 resistance at 121.95.
If the price respects a zig-zaggish standard retracement pattern, it could drop towards POC and reject from there. The zone is 120.15-30 and as long as the price holds above 119.30 the targets are 121.95 and 122.80 if we get hourly or 4h close above 121.95.
