I wish I could say that Japan has a plethora of great shaving gear from anywhere! I'm far from Tokyo where there might be more options, but here's the situation out here in the boonies.
Loads of cartridge and disposable razors, Gillette, Schick and several Japanese companies, all desperately adding blades and power units and lube strips. Hardly even any choices of canned goo. Gillette rules the shelves. Usually there is one lonely pack of Feather DE blades and the same 2 brands of aftershave, Auslese and Bravas. Lots of cheap shavette type blades for styling. Very hard to find Kai blades or Feather DE razors...in fact I've only seen them in a cutlery shop. Japanese men tend to have pretty sparse beards, so electrics and cartridges seem work decently for them, even considering the prices. I work in universities, and very few of my male students look like they need to shave more than a couple times a week, if that.
I get everything from the US (loaded up when I went back on vacation) or the internet.
Straights are very rare here, and I would almost bet that more Japanese razors and hones are sold in the US and Europe than in Japan. I've never heard of anyone who uses one and have never seen one for sale. Same with brushes.
So if you are coming to live, load up on the soaps creams and ASs before you before you move.