I got back from a Japan trip a couple of weeks ago, among many highlights I bought a frame and some parts (which is what inspired me to re-join this forum after a few years of being slack and not riding bikes much! Hello to everyone).
I can post some pics if you like, long story short:
Went to the Keirin in Kawasaki, very interesting experience with $1 entry and dog-track atmosphere, yet the riders are world class.
Went to a lot of shops: Hippies Mart, 25Las, Blue Lug, Tempura, C-speed, Giracha are some of the names I remember, I think we went to 7 or 8 Keirin related shops. Very difficult to find and most times we were pointed from one shop to the next by the shop owners. All were very surprised by our enthusiasm to Japanese bikes haha and super friendly/helpful.
Rode 500-ish km from Tokyo to Osaka, stayed along the coast which was great, only one killer hill section through Hakone, then bullet train back. Super enjoyable ride with no stress or drama, took 5 days at a cruisy pace (riding ss not fixed!)
My best advice would be to take a bike over there and ride it around everywhere like we did (not much of a drama going through the airport, bit of a struggle carrying bike bag and suitcase on the train though!) and if you want to go to the shops try to make contact with some of them first through email or facebook, they love it! Also we had a pocket wifi so we had google maps the entire time which was absolutely essential, I don’t think we would have found half the stuff we did without it!