Hmm. That's quite interesting.

I was scheduled on NRT-TPE later in March on NW 95/96 but my reservation only shows NW96 changed to NW6 from TPE-NRT while NW95 NRT-TPE is still the same flight number, which means the change takes place sometime in late March.

From the looks of it, NW 5/6 are currently the NRT-PUS (Busan, South Korea) route. On the day that my flight got changed, NW96 changed to NW6 while the original NW6 changed to NW86. It also seems that NW5, currently from NRT-PUS, is changing to NW85. Doesn't look like NW 85/86 are currently assigned to any flights, and who knows if 95/96 got assigned to anything?

So, from what I can tell, NW95/96->NW5/6 while NW5/6->NW85/86.
The reason for the change? Who knows? Maybe it's for some big Asian routing/ flight number changes.

I'm assuming your flight goes through Portland because that would make NW5/6 a direct flight for you. Bummer... Maybe you can take NW1/2 from LAX, or route through SFO or SEA next time? That way it won't be "direct."

But for now, maybe you can ask for original routing credit or to be rerouted through another city because they imposed as "schedule change" (even though it really wasn't much of a schedule change other than flight number).