CFI,
I've JS several time through NRT both on UA and NW - here's the deal. No, you will not have to exit the secure area in NRT, but as others have posted, you do go through another security screening. There is a simple way to get through the whole deal - wear your uniform. Not only are you exempted from the liquid restrictions (they have the same as the US), you get escorted to the front of the line and won't have any questions or hassles for not having "a ticket". Walk over to the UA transfer counter and sign up for the JS. They know exactly what they're doing and I've never has any problems. The counter is almost always staffed - unlike the gate which will open only 60 minutes before departure. My personal technique was to bring a light weight generic pull-over sweater to wear once you're onboard (I prefer to be on the D.L.), and only be in "full uni" to get through the transfer security and for checking in. Works like a charm.