Japan figured out currency manipulation as the key to winning global trade in the 80s with ZIRP and keeping their currency artificially weaker than the dollar by building up FOREX reservesYou sure about that?
Looks like they started the 80s with 250 Yen to the dollar and ended the 80s with about 150 Yen to the dollar. Now they're 80 Yen to the dollar.
If they have a weak Yen policy, they must be doing it wrong.
China undercut Japan to takeover the trade crown from Japan in the 90s, as they merely duplicated what Japan was doing on a much larger scale with the USD/Euro. China made sure they were the cheap supplier of choice in global trade by also keeping the Yen strong.
The yen is only 4% of world FOREX reserves, so it doesn't take much to maintain a strong yen vs. the dollar as part of China's FOREX strategy. This is one of the reasons Japan is not happy with China. On top of that, the FED is also helping by devaluing our currency. Japan is basically a bantamweight between two heavyweights fighting it out.