Plane arrived around 5:40pm. JAL came through with the airport escort from baggage claim to the gate, and SO ended up in F on the 7:00pm to ITM. Still had to go through the regular visitor immigration line and didn't reach baggage claim (where of course, the bag had been waiting for 20 min) until 6:15pm, so potentially some room for improvement there.

JAL agents actually had the checked bag brought through domestic security and checked at the gate. It also turns out I had been intending to fly with my SO, and the agents had no problem switching my ticket around to accomodate whatever flight necessary (as long as the flight was at least Y1 or J1). Overall A+ service.