Now I have another problem...

The flight in question AA154 NRT-ORD shows in EF as C2
AA154 NRT-BOS shows as C0
It somehow makes sense, as ORD-BOS doesn't have a business class, so it can't have C inventory.

Now would it be better for me to let my travel agent split the flight into two segments so that I can grab the UG on NRT-ORD, or will it be possible for the EXP desk to confirm my upgrade on the 'direct' NRT-BOS.

PS: AA154 ORD-BOS is showing A7 as well, so the upgrade on the domestic would be available.