American/JAL, Delta, United/ANA all have Los Angeles to Tokyo Narita NRT and Haneda HND on sale for $469 round trip for travel departures from November to March 2018.
Fares on Momondo may be $15 to 20 less.
American Airlines Los Angeles LAX – Tokyo NRT
Delta Airlines Los Angeles LAX – Tokyo HND
United Airlines (ANA operated flights)
Los Angeles LAX – Tokyo NRT