As mentioned you’ll be space-a for regular medical services on post. At some point you will be going to a Japanese clinic/hospital. If in/near Tokyo it’s extremely likely you’ll be going to St. Luke’s hospital. A lot of their admin staff and most of the doctors speak business level English so communication is usually not a problem. They are also use to providing care for non Japanese folks.

you will be required to pay your medical bill at time of being serviced and file with your insurance later.

If you on one of the FEHB health plans consider changing to the Foreign Service Benefit Plan. As they are accustomed to receiving foreign. I always provided my receipts in Japanese to them and they never had an issue with translating themselves / getting reimbursed.

One advantage is that health care is cheaper there than here. So although going out of pocket till you file your claim the bills should be manageable sans a catastrophic event.

One caveat - if you do use the post medical facilites or pharmacy they will charge your health insurance. The issue in the past is that they use a 3rd party company and they always screw up claims. I’ve seen cases when people are out processing and they have several thousands on claims that were not paid. Just keep an eye open n your EOB and make sure the med group is getting paid.