@user5924704 , on rethinking through your situation, it may be simpler if :
(a) you file the form 1040-NR, recognizing the award income
and thereafter,
(b) you file your Japan return normally, recognize the award income and then seek Foreign Tax credit ( from Japan ) per the tax treaty. While I don't know the mechanism / form to use, the fact that you are a resident and citizen of Japan, would allow you to claim Foreign Tax Credit in Japan. And much easier probably ( also because your local tax professional can help easily ).
Is there more I can do for you ?
