Singapore Airlines has LAX to Tokyo NRT at $499 round trip for flights on several dates in January with a few dates in February and April 2018 and more dates at $549 round trip.
Singapore Airlines LAX – Tokyo NRT nonstop
$498.97 round trip Tue Feb 27 – Thu March 8
Ticket books in SQ economy K booking code earning only 10% miles in Singapore KrisFlyer, SAS Eurobonus and Virgin Australia.