The alternative:

Arrive in Japan. Enjoy your day until you're tired.
Take a nap.
Wake back up...go about your day until bed time.
Ambien.
Wake up the next morning with your body clock on Tokyo time.

If you've not taken ambien before, a Japanese hotel room is not the place to start.

Your results may vary. Most of my travel is short-notice and for only a few days at a time, so ambien is my "circadian rhythm defibrillator".