Hi there, hope someone can help with my case.

I'm planning on transiting NRT with separate tickets, which I understand is completely fine.
However, my originating point will be DEN and I'm a little unsure if that will cause any issue.
My backup plan is to first fly from DEN to LAX or somewhere else on the West Coast and then fly to NRT.

The route in question is:
DEN-NRT (UA), then NRT-SGN (ANA Business booked via VS awards)

Does anyone know if the UA agents in DEN are aware of the possibility of transiting NRT?
And would I be able to check my bags through to SGN?