Really interesting you buying things from Japan and making it look so easy David. Lol... It makes me anxious just doing the searching!
Out of interest, is Buyee actually the Japan version of Ebay and would you consider buying power tools from there. I'm going to assume that things like Makita would be from their local manufacturing plants and not the China ones, but anythings possible I suppose.
Currently after upgrading my impact driver from the falling-apart Metabo...
Macca pretty much hit it - it's a proxy service. As you found, in japan they like to use yahoo's auction here. Ebay dominates here, but didn't catch on there and for some reason yahoo did. Fortunately, the auctions are open to everyone, so you get the same treatment as someone buying in japan, which is important.
In terms of the buying, you kind of have to learn the ropes by knowing what you're buying, and not just buying immediately because something looks like a good price in the USA or europe. For example, $20 maebiki saws in good shape is a common thing on buyee. The same saw may be sold on ebay here for $250, and you might find a listing for $125 on buyee and perceive it as inexpensive. But you'll probably want to combine it with other things and ship it surface - saws are tough, surface mail is a rough way for packages to go, but no problem with a big saw. So figure adding $30-$40 in total costs for allocated shipping and package combining.
The other unpredictable part lately is two-fold:
1) shipping to various regions is hit or miss. We lost EMS for years due to covid, but other methods ship. then, I bought a bunch of cheap stones in a pair of lots figuring that I could have them combined and given protective packaging and sent surface for a total of about $50. I ended up having to ship them DHL air for reasons that I can't guess. That was an extra $50 more or maybe silghtly more than that.
2) there seems to be a big increase in restricted items. I've had one single item that I got unrestricted and then when they received it, they changed their mind (guitar with madagascar rosewood fingerboard), and let me know that I could have it sent in country or destroyed. Those aren't great options. Fortunately, stu tierney still lived in japan (I've known him longer than his store) and he sent the guitar to me after having it shipped to him. They were worried about something that is no issue in the US in practice, and now by cites revision, it isn't by compliance. Brazilian rosewood is trouble coming into the US if it's marked, but customs has never bothered even infills that come in with it if they're old. The shippers will often seize it themselves, though, out of fear.
The bidding system for things over there is easier than ebay - instead of making a permanent bid, it's a proxy by default. You line up what you want and then remove the bids later. It doesn't bid until the last minute or seconds, don't remember which. It's a lot easier to keep track of.
There are other shipping services - customer service in japan isn't like US or UK, either, so keep that in mind. Whatever their rules are at the time, they're not going to move, and you may not know them. They ran out of guitar boxes at one point and I ended up getting a guitar in a giant box which they only described to me as "the guitar is oversize, so we can only ship it DHL" which doubled the cost over EMS. When I got it, I realized it was only the box that was large and when I asked if they were going to get regular guitar boxes again (Figure a difference of $200 in shipping), they didn't respond to the question with a reasonable answer.
But, all in all, there are things you can take advantage of if you're willing to look at the cost benefit over the long term. For example, used high quality chisel sets for $100-$200 (sets of 10 or more). You can find those one a week and they're usually better than what's $80 per chisel sold to the west.
