So I'm going back for the third time, aiming at late autumn 2019. Last time we spent two weeks in Tokyo but we want to do more stuff and not be quite as shopping focused (especially for my friend who is not a big shopper). Might try for three weeks but less shopping. Tokyo would be one of the weeks with maybe three more major places to visit over the other two.
What I really, really want to do is go to a concert with any of my big three current favourites: Sarah Alainn, Leo Ieiri or (if they're touring again already) Ikimono-gakari. How likely am I to hit a concert within a three week span? I might want to go to the Mitsuda concert on November 3rd, but that's a bit later than I had planned to go. Ideally I want to see some autumn colours since both previous times were in April.
I've also been to Kyoto and Osaka previously so I don't particularly need to see those again, although I never really went to the iconic Osaka sights (except the castle which sucked). I have to admit that Abroad in Japan is selling me on the northern parts of the country. Sapporo might be a bit too much but Sendai could be nice, although possibly not late in the year? Maybe do Kyushu and then a Hiroshima -> Nara trip, although it would take a damn long time to get back to Tokyo. How is that area in October/November?