Not sure what your budget is but you can book a roundtrip YVR-NRT in business on JL for ~$3300, outbound March 27 with return sometime later that spring. Book a separate ticket up to YVR.

I also see a one-way LAX-YVR-NRT for $2k but it looks like you have to book it as WestJet flight numbers, which may or may not be of concern depending on if you're going for AA miles/LP's or not.