Lovely piece! Any thoughts on whether or not speaking Japanese would be a requirement? It would of course be the polite thing to do.
One thing that I didn't expect (although it makes perfect sense) is that OCR of Japanese writing is very bad compared to what we've got used to. Aiming a phone with Google Translate at some sign will often produce total garbage. You can attempt to transcribe the kanji with your finger and that usually gives better results, but is tedious and difficult (since the order of strokes matters and you have no clue about it). We've quickly learned a few crucial kanjis, e.g. 出口 for `exit`.
A tip for the restaurants that only offer japanese menu with no pictures: open the listing in Maps, browse through the photos and show the waiter a photo of the meal you would like.
Once was with other foreigners at a hostel. But the other time it was at some tiny pub in Hiroshima. They had like 3 tables and there were only the owners (a couple) and 2-3 regulars. All of them wanted to drink and hang out with us and they were very loud and enthusiastic even though we didn't understand each other almost at all. We loved it, I will never forget it.
Hmm, or perhaps some other subculture which addresses both language overlap and (sub)cultural openness? Like local alumni, or some software-related community (eg ruby, or XR, or ...), or ... ? HN people? In context of TFA, perhaps something surfing? One dream the net was weaving a world where you could have a friend in every city.