Edit: I stumbled on this nice site recently: willmyphonework.net, which allows you to check compatibility of a lot of phones in various countries. It confirmed my iPhone 6S also works in Japan.
And now for something slightly different (still tech related), I went to Japan this summer (btw, I wouldn’t recommend that: go in spring or autumn) and wanted to use a sim card in my unlocked iPhone 5S (model A1457) and wondered if it would work.
Different sub-models of iPhones have different antennas (GSM/UMTS/CDMA/LTE etc), which means an iPhone bought in one country may not necessarily work in another country due to different standards. So I tried to find information on this topic but couldn’t find confirmation on whether the A1457 model would work in Japan.
Well having been there and used it with the U-Mobile (NTT Docomo network) sim card I got for it: Yes, the A1457 does work in Japan with both LTE & 3G. I had no problems using it in Japan even in somewhat remote areas.
Now fortunately newer iPhones (6/6S) are a better kind of “world phone” than the iPhone 5S was, so I should have no trouble in the future either.