United, ANA, and Singapore Airlines have round-trip flights from Los Angeles (LAX) to Tokyo or Osaka (NRT/KIX) for $475-$500. Flights October to May. No Weekends. Departures on Monday, Tuesday, Wednesday, and Thursday.
Note: Flights to Tokyo are NONSTOP. Flights to Osaka require a connection.
Note: Some small OTAs on SkyScanner have this for about $438. If you plan on booking there, beware of any site that charges a fee to cancel a ticket within the 24-hour “free” period. Use unknown booking sites at your own risk.