Bikes would not be my first priority, I would try to visit as many of the cultural sites IMHO Going to Japan for parts is a missed opportunity.
from the web: https://theculturetrip.com/asia/japa...eritage-sites/
Kyoto, Narhara, Shibuya, and many others....of course, I would stop on my way to visit a few bike shops....check the local for sale to get a 3Rensho's along with a few Keiren track bikes to ship back and help pay for your trip!
P.S. I need a set of front and rear discs for my Bertoni. 650 front and 700 rear.
Enjoy your trip...Best Ben