tricare wls and being overseas
OK, So I don't actually know the answer to this one, but I was a Corpsman, so what I do know is they only offer bariatric surgery at the largest of the Navy Hospitals. I'm skeptical if Japan would have a Bariatric program at their hospital there. It should be easy to find out just call the hospital & ask. That said you might be able to work all of your preliminary stuff there through your Primary Care DOC, get a referral and see if you could get assigned to a surgeon here stateside who can tell you what there requirements are and "maybe" you could get it done from there. But this is entirely hypothetical, Only the hospital or your doctor could tell you if it could really work?
Good Luck!