"Got any idea what keeps the yen strong?"

David Fuller's view The flippant although not inaccurate initial answer, as you know, is more buyers than sellers. Although not today, as you can see from this chart of USD/JPY showing the dollar rallying from just above ¥82. As you can see, that was an initial support level. A break above ¥84.5 would reaffirm the short-term recovery.

Returning to the original question, I think many people have lost faith in the BoJ's ability or will to weaken the currency. There are probably some internal politics involved but I would not underestimate the BoJ's ability to weaken the yen if economic pressures to do so determine policy, as I believe they will.

Every central banker knows how to weaken a comparatively strong fiat currency. Persistent jawboning and intervention will usually do the trick but the BoJ may regard that as too western or they may not wish to risk losing face. The foolproof way to weaken a currency is by turning on the monetary printing presses. The markets will eventually notice.

My spread-bet USD/JPY long expires on 10th December and I will roll this position forward. It is not that I like the USD, but at historic lows against the JPY, I like it more than the Japanese currency. Double bottom, anyone? That is what I am hoping.