But Sir, AA can't check bags to NRT unless you are eligible to enter JPN; that is why I see a risk that either AA will refuse to tags to NRT only or even refuse to bring you to NRT because you don't have a (confirmed) onward flight.

But anyway I'm just guessing; not first hand experience with standby tickets and how they are dealt with. Good luck!

Do let us know how you solved this/how is plays out at NRT.