s1c3r1a1b3b3l1e1's advice is good.

I would add that Delta also flies LAX to both NRT and HND. Check both for possible awards even if Korean is cheaper for the one ticket you are going to buy.

Korean also flies nonstop LAX-NRT, not necessarily every day. You can check their schedule. Both are bookable with Delta Skymiles.

I agree with concentrating on LAX as your anchor city for going across the Pacific Ocean. Add LAS-LAX, if possible, when the reservation agent finds your friend redemption space on LAX-Tokyo