(1) no interest-arbitrge argument;
(2) Japan's trade position DETERIORATING;
(3) US and Japanese monetary authorities undertaking broadly similar jawboning, but US Fed actually 'tapering';
(4) capital outflows (foreign net selling of Japanese stocks).
So on any sensible theoretical basis - UIP, Robinson-Metzler-Bickerdyke or money-stock-growth conditions - JPY ought to be weakening.
My guess is that it's a hedge fund that's blowing up - having gone long USDJPY and NK at recent swing highs, they're now dumping NK and USDJPY . That is, the same story as happened in Crude at 147 (and again a year later, at $33, in the opposite direction)