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