Sorry for the delay, we have bad winter roads up here so it takes forever to get anywhere.
Like FTMax said, I was in Japanland for 4.5 years. My first question is where are going? Second, are you on any injections? If you're just doing oral medication you will need to get a doctor's note before you travel that your medication is medically nessecary. You can bring a 30 day supply on a tourist visa and an 90 on a work visa and have the rest mailed to you in 90 day supplies, but there is a form you will need to fill out and turn in to customs at least one month in advance. If you're in a big city (I was in Osaka) you can turn it in locally. I was able to turn mine in at the Otemae offices, but it still had to go to Tokyo main office for approval. If you are in inaka then you may have to go to the city hall in some cases. If you are on any injectables (insulin, vitamin D or anything like that) there is an additional form you need to fill out at least 2 months prior to importing any needles. This also applies to epipens. I can dig up the form later. It's buried in my legal paperwork. But needles are illegal to own and I had to jump through hoops to get mine.
Both of the forms I mentioned need to be filled out in Japanese and have a copy of a doctor's note and the prescription attached. If they are filled out in English or another language there could be a delay in approval. Once you have the approval, it will need to be attached to the package or you will have to fax them after the packages arrive in Japan. I only needed to do it twice, but I have heard some people say they needed to do it much more often, even for things like depression meds, simply because their local customs offices were not as organized as the larger cities. There is also not a lot of foreign language support in the government offices, so you may need help filling those forms out. I was able to do it, but I still had a trusted friend take a look at it.
If your japanese is good enough to navigate the medical system and you live in a large city (Tokyo, Osaka, Hyogo or in Okinawa) there are doctors that will treat you. My situation was more difficult in that I needed an injection monthly and by the time I navigated the system I only had another few months, and it would have still taken a few psych appointments and a physical (about two to three months) to get my medication so it wasn't worth it. If you are near a larger city you may not be able to find a clinic to treat you. The system is pretty outdated the further out of the hubs you go.
A third question is do your IDs have your correct gender marker, or will they before you go? If not, carry your doctors note. If your ID does not match and you need to seek medical attention, they won't care that the letter is in English and will take it at value.
All that being said, it's a lovely place and I sorely miss it. We came back for family reasons and economic reasons (don't get me started on Abe) but we have talked about going back sometime in the future. The people are very helpful but they are unable due to the system to think outside of the paperwork box. They still physically stamp things and mail them over fax and email. But, I was never treated poorly and the few interactions that were uncomfortable were because I stood out quite a bit. I'm blond and blue eyed with tats ans piercings so I got a lot of stares and people randomly touching my hair because it's good luck with older folks. I would caution against onsen and bathhouses. Many will not even allow foreigners in it can lead to some discomfort.
If I forgot anything or you have any questions, just ask.
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