I still have unpaid phone bills from when I studied abroad in Japan. Will their collectors find me in the US? What happens if I ever return to Japan?

After studying there in the spring and summer of 2008, I owe quite a bit to Softbank Mobile for a phone that I took the liberty to take back to America without their authorization, and KDDI Mobile for using their discount service to make international calls.

I would have set up a forwarding address back to the United States but was informed that Japan Post doesn’t forward mail internationally. Therefore, I never got to see my phone bills ever again.

So as my unpaid bills fester across the Pacific, will the Collections departments of Softbank & KDDI find me in the United States and report me to the 3 major credit bureaus here? (Experian, Equifax, and Transunion)

Or will they only act if I ever turn up in Japan again?

For example, if I successfully join the Air Force, I may get stationed in one of our three air bases in Japan (Kadena, Misawa, or Yokota). Therefore, when I disembark from my flight at an airport, I’ll be face-scanned, fingerprinted, and passport-swiped. When that happens, will an alert show up in the system that causes them to arrest me for non-payment?

(Or if I don’t join the Air Force, I could be in Japan for a pleasure or business trip some time from now.)

Anyways, when I first got my keitai, I believe I used my gaikokujin tōroku shōmeisho (alien registration card) to register myself as a customer for their mobile service. (Hopefully not my passport.) I had to surrender that card when the semester ended and I was about to board a ship to Korea. I think Softbank only has my registration card info, so if that’s the case, then I can keep getting away with it, can I?

(But if I registered with them with my passport, then they’ll find me, won’t they?)

Lastly, if I get picked up by the law at any of their airports for this reason, what other sanctions may they hand out to me?