If you are a travel companion, just book yourself into J, if there's a seat when your number is up, you'll get it. It's not really an upgrade, you book yourself into J and you pay the fee for that class of service. There are no elite upgrades to NRT, only paid tickets and mileage upgrades, so if it looks like there's a lot of seats 24 hours prior, you'll probably be able to snag one.