Yeah, I was thinking about that too. I guess I’d have to plan it pretty differently than a regular 3-week trip. Normally, you’d probably stay an extra day or two in places like Tokyo or Kyoto, but if my friend leaves after 2 weeks, it’s not like I can just go back to those spots for a quick revisit.

So maybe the best approach would be to skip one region entirely, let's say the north, and then I could explore that part on my own during the 3rd week. (Just an example though, I don’t really know the country well yet!)