Call NH and ask to be changed to NH005 (LAX-NRT). With status and the right agent it could be a win-win. I know it is a different city. The odds are not good, but with status it is possible (I have done it many times).
NH005
Flights operated by ANA Group (ANA[NH]/Air Japan[NQ]/ANA WINGS[EH])
Los Angeles Tokyo(Narita)
11:30 16:25
+1 11:55
Economy
Seat Map
77W Seats available
From OP: If I SDC LAX-SFO flight to the last flight the day earlier, can I stay at lounge at SFO that night?
No. The UC closes. Also, can you SDC the day before?
Perhaps you could call ANA with your "story" why it is "imminent" you fly from LAX to NRT and not take UA LAX-SFO than ANA SFO-NRT.
You never know. Without status, I doubt it.
Perhaps your plans changed, but who is your travel agent?
Call ANA - they have always treated me fair.