The author is implying that BoJ can/might/will cause appreciation of the Yen, which will force folks who are short(borrowing Yen) to buy USD assets to go underwater, forcing liquidation to pay back the Yen, and appreciating the Yen more. It's possible but there is no guarantee it would be a disruptive feedback loop or this year or etc.

If you believe them, then you can hedge buy either shorting TLT(betting treasury yields will rise), or going long Yen (e.g. FXY shares/calls).

I bought some FXY calls but just enough to hedge the Yen prices of my upcoming Tokyo trip in case they're right.

We are profoundly fucked.