Has anyone ever bought a camera in Japan? These prices seem pretty good (some 700 euros for a K-3ii, which is an atarashii/new one)
(??)PENTAX (??????) K-3 II ??????ID?4549212294006?????? | ??????????????????????????????

Obviously involves a trip to Japan but that would sound to me like killing two birds with one stone

Are there any obvious caveats like not being able to set the UI to English or being given the "wrong" kind of plug/current for the charger?

[Zooland]

You could check out Yahoo Auction, if you can pass the hurdle of creating an account with them.
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[Komainu]

I second the Yahoo Auction option, just got a great deal getting an old lens with barely no japanese knowledge. Google Translator is not perfect, but it is possible to understand most of the process.