This is likley to run out of steam soon, ...

TVC:NI225   Nikkei 225 Index
too. - But not before US Equities do!!
(Made a lot of money on these longs until now and especially being Short DJIA/Nikkei225 Spread!)

... and given the currency differential, the Nikkei225 is still a helluva lot better deal than US indexes.
Here is the SP500 /Nikkei225 Spread
Short it until it can be shorted no more!

Here is the Weekly;
Comment: Also ...
... the DJIA/Nikkei225 Quarterly chart. The Best SHORT out there, bar none!