I've got a general question regarding travel on United. I'll highlight a specific example:

I'm looking to travel from SFO to NRT (Tokyo) in July. Fares shown are approximately US$1,800 for a non-stop flight both ways. Leaving on United 853, and returning on United 852.

I was curious to see how much fares from LAX would cost. I found that there is a fare that costs approximately US$1,300. This trip is as follows: LAX --> SFO, then SFO --> NRT on United 853 (same as above). The return trip is NRT --> SFO on United 852 (same as above), then SFO --> LAX.

The question that I have is can I go ahead and purchase the LAX to NRT ticket, which stops in SFO? I completely forfeit the LAX legs because I live in San Francisco. I'm only intending to have my personal bag and a carry on, with no check in baggage.

And I was curious to find out if this applied in general terms.