Makes no sense to me either - presumably something could be attributed to the values of the Japanese stocks trading on other exchanges.
Toyoda Motor ADR's are up over 1% on NYSE now while in Japan it lost 4.6% last night. It is like the Japanese market crashed last night but bounced back higher after Tokyo closed.
I can only speculate that there is some options/derivatives based demand that is triggering purchasing on exchanges other than Tokyo today.
The EWJ is NOT tied to the Nikkei Index, but instead to the MSCI Japan Index Fund.
Also, overseas ETFs may be subject to effects from currency fluctuations (particularly the recent volatility in the Yen) more so than ETFs based on US Indexes or Sectors.