You've been emailing and writing for four years... wow. Feels like you would know by now from the various signals you might be sending each other, what your intentions are.
And what's the situation with the long-distance romance? You met online? Was there an expectation that the online meeting might result in an escalation of affairs? And this real-life meeting...how did this come about? What were the circumstances? Proper adult dating situations, or was it like some platonic "let me show you around Meiji Shrine and then have a quick coffee before we go our separate ways" sort of thing?
Seems like there is a lot of info missing that might help make a decision.
If everything is merely business, and there is absolutely no indication that she is expecting anything further, then you are probably already in the friend zone, and just enjoy that relationship as it is.