That is the line in the sand....
The USDJPY has moved lower in trading today but also had some volatility on the back of GBP volatility that whipped around GBPJPY (and with it JPY). Technically though, the price moved below a support line in the sand for me at the 106.237-425. That area has had a number of swing lows going back to the end of April (see blue circles).
Staying below that level is more bearish. Move above it and the gig is up.
You ask "it has already moved back above it today?" Correct. But that came on the Brexit rumors. Can it happen again? Yes. It could so you have to protect yourself on a move above (that is assuming you want to be trading now).
Remember as well the Fed decision is ahead and we are still above the lows at 105.72. That is the battle that have yet to be won from the short side. However, if the price action can keep below the "yellow", the sellers have a little more advantage. Move above and all bets are off.