Also I forgot to add - I fundamentally like holding UJ due to the FOMC and BOJ Monetary Policy Divergences...
At the moment the FOMC is into its hiking phase where it is increasing the interest rate, which in turn, increases $ usd demand (hot money seeks the highest interest rate). The hiking phase is also warranted IMO as the US economy is nearing full employment ( as many key Fed memebers (e.g. Kaplan) keep ephasising). Also inflation is nearing their target.
On the other hand, BOJ is undeniably easing, since their economy has weak inflation (-0.4% last print) even after years of easing, so my expectation on the BOJ tone for the coming future is dovish.. such policy decreases the value of the JPY as by QE and low rates, it encourages the money supply to increase.
So to summarise, we have the FOMC USD hiking, increasing $ demand, and on the other hand we have BOJ easing, and increasing JPY supply.
Increased dollar demand = BUY dollars, and increased JPY supply = SELL JPY; hence why BUY USDJPY makes so much sense fundamentally also.