All honesty, I would be a little careful buying gens in Japan.
I actually happen to live in Nakano so I often check out the grey market stores.
They do have nice unique pieces at quite reasonable prices, but I would be a little weary about the pieces in the movement.
Why?
Answer is simple. I wouldn’t buy a watch from there unless I first confirm that the watch is still covered by factory warranty; Meaning the watch has only ever been serviced at licenses dealers.
There are many talented watch makers here that do work on gen watches when they need servicing/repairing and when they do make replacement parts, they aren’t always of swiss eta quality pieces. Many people here use these watchsmiths just thinking they are saving a boatload on both time and money to have thier watches fixed/serviced.
Call me paranoid, but if I am shelling $20,000+ on a watch, I’d like to know that every part in the watch is genuinely from the original factory.