If they're flying from NYC you might want to get them to stay out late the night before, give 'em some good travel pillows so they crash hard on the airplane, then wake up at something close to Japanese time. Late morning in New York is bedtime in Tokyo, so falling asleep after a late morning takeoff will have them almost precisely where they need to be upon arrival.

If they're still groggy after arrival look into a kind of chewing gum called "Black Black"--you'll find it in the convenience stores and it's basically chock full of caffeine. That should bring them back from the dead...