I have observed a possible of JPY appreciation as it is spotted across EURJPY, NZDJPY and CADJPY the only thing they have in common is JPY. Due to uncertainty of the market of the following:
1. US-China Trade War pretty much affect Australia
2. Brexit deal affect GBP and EUR
Investors may flood their cash into JPY as Japan did have the thoughts of removal of the negative bank interest rate, that may cause JPY surge.
Just the thought of no further action of today causes JPY appreciation across many major currencies.