@artskool sorry for the tardy reply mate, shit has been busy! I think a speedy reduced would be a great watch to pick up here, they are always in good condition, prices aren't as cheap as they were even 3 years ago though... Black bay 36mm aren't as easy to find, at least the older ones aren't, and the price is going up. I shouldn't have sold mine so cheap!
Here's some places to go (be aware I haven't lived in Tokyo in over 20 years so I'm probs not the best person):
Ginza: obvious first stop, not so many vintage stores (except maybe Quark and the like) but there is a Seiko museum there (that I have never visited)
Nakano: Hard to describe how to get to the Broadway building, but just punch this address into your maps:
https://www.jackroad.co.jp/shop/pages/company_new_en.aspx Once you find Jackroad, you're in the right place. They have a massive selection but the prices won't be that great because a lot of tourists frequent there. Their sister store also has some good finds and they aren't always female only models. There's tonnes of other watch shops in that area that I'm certain someone has written a guide on so maybe do a quick search on google.
Random pawnshops and Camera Stores: Daikoku-ya is a famous pwan shop and they have stores everywhere the stock they have will differ from location to location so not very effective, but always always good to stop by if you see one on the way to somewhere. Big Camera stores often have a whole floor dedicated to watches too, but they'll probably be new. The same goes for big department stores here; they'll sell all the latest brands, but not too much 2nd hand in most cases. Don Quixote is a really random store that sells everything, but some of the bigger locations have 2nd hand watches. Again, don't seek on out unless you're on your way to somewhere and you happen across one.
Next up, some random shops that will defs be worth hitting up:
Again, Jackroad has a REALLY good selection so you might be a bit let down by the smaller places, but they will have better prices and also rarer/ less sought after models.
Eguchi -
https://eguchi-store.jpAbitro -
https://arbitro.shop/en/collections/vintage-watchesFirekids
https://firekids.jp/collections/all?pf_st_fan_mai_zhuang_kuang=in-stock(is in Yokohama from memory but not that far out of Tokyo)
Time anagram -
https://timeanagram.com/en/collections/frontpage(I think you need to reserve before you visit which seems like a pain BUT their selection is MINT)
Curio x2
https://curious-curio.jp(lost of military style watches)
These two also hit up a lot of shops, so just check their vintage vids for shop names/ locations:
https://www.youtube.com/@watchspiritstokyo.5188/videosI would also trust worn and wound with their choices:
https://wornandwound.com/hunting-vintage-watches-tokyo/