suddenly jump so much.. what happened har?
A combination of:
* Japanese retail FX punters (remember Mrs Watanabe? apparently she never left) being long a truckload of TRYJPY on margin, with stop-loss levels close by;
* Lots of USDJPY RKO barrier triggers in the 105-106 region;
* Low liquidity in the witching hour: NYC's gone home, but Tokyo and Singapore haven't really opened up yet, so the only people trading are Sydney (and Auckland, but really c'mon the Auckland FX market is literally four guys);
* Even worse liquidity in the Turkish lira, because it's after midnight in Istanbul and nobody in their right mind is trading Turkish lira at those hours.
If you're really bored I can nerd out on the exact mechanics, but my guess is that a few stop-loss sell orders going off in TRYJPY sent it lower, setting off more stop-loss orders in TRYJPY, which pushed USDJPY and AUDJPY lower, which set off even more stop-loss orders and option barriers; bank traders had to sell USDJPY and cross-yen to fill their stop-loss orders so it just kept going until some actual humans woke up and said "wow why is yen so strong, I'll sell some"