Well, honestly, I'm not sure I'd go with a castle but I guess that's really only a few steps up from my first thought.

[His first thought being something similar to his own home back in Japan: a very large, traditional style estate.]

So I'd go with something Japanese. You know, like Osaka castle or something. With modern comforts on the inside, of course. [...] Well, as modern as this place goes, at least, if our idea of modern isn't doable.

[Because who wants to live in a drafty historically-accurate castle? Not this brat.]

Much classier, in my opinion.