I'm not sure about the takuan part, but I got asked about the "Japan smell" recently myself. My guess is that the teacher meant "I heard foreigners can smell a distinct scent of Japan as soon as they get off the plane," or something along those lines. (And I have actually heard some people say this, but I have no clue what they're talking about.) At any rate, that's what Masaki-san asked me. Only I said I never noticed any smell and we laughed about it actually being the smell of the airport that they were talking about.