Historically Japanese (and other Asian) airlines have hired US pilots on a contract basis through one of a few contracting agencies. Not sure available that is for the Japanese companies anymore.

Those contract western pilots are not "regular" employees...I think they have a typically five-year contract which can keep getting renewed as long as they need you. To become a regular employee would probably be very hard indeed for a westerner.

But you typically need time-in-type, probably captain time.