Stinger is pretty much right. Here's a brief timeline of broadband:
Late 90s: Cable and DSL start popping about in the US. Japan offers cable, and cable only, and only in a very few remote parts of the big cities. All in all, only a handful of people have it, and everyone is screwed paying NTT big bucks.
Sometime in 2000: Not sure when it started, but Toyko Metallic (東京めたりっく), Japan's first ADSL provider succeeds in suing NTT, and DSL in Japan is born. NTT must now lease their lines out to DSL providers. Gaijin Punch is one of the first 10,000 customers in Japan to get DSL, and pees in his pants on a few occasions. Tokyo Metallic's speeds were roughly 1.5 Mb download, and 768kb upload. Price runs about 4000 yen per month, and 15,000 yen installation fee.
NTT's claim was that they would skip DSL, and go straight to fiber (trying to protect their ISDN investment, which they apparently lost millions on). Note that to get DSL installed, NTT might have to come and change your line from one type to another. The installation is actually a hassle.
3 months later: NTT, as well as another provider (forgot who) now offer DSL. NTT is charged with doing sneaky things. Remember the aforementioned work NTT might have to do to give someone a line capable of DSL? Well, sometimes they'd just go ahead and sort out an NTT DSL connection right then and there, c-blocking Metallic or any other 3rd party provider.
Within the next year or so, speeds are getting to around 3Mb download and 1MB upload.
Not much later, Yahoo BB comes out, and offers up to 8Mb download. You had to be pretty close to a hub, but it was still good speeds.
-In either 2002 or 2003, Usen comes out w/ their Hikari Fibre connections, and introduce massive overkill to the broadband market. 100Mb download, 10Mb upload, and 5 WAN IPs. All for personal use. O_O. NTT jumps in w/ their Fiber stuff not much later.
Basically it took Japan forever to get DSL, but once they got it, it took less than 2 years to surpass the US, and likely most of the rest of the world. I tried Usen for a while, but I don't use antivirus or anything. They called me ALL the time telling me I had spyware and virii and whatnot. Annoying. When I moved, I changed to Itscomm, w/ a 30 down, 10 up connection, which was just fine.
The Tokyo Metallic thing is pretty interesting. I'd love to provide you with a link, but unfortunately can't. For the record, the CEO was a former NTT executive. Basically tore down the empire he helped build. He knew the company would fail, but he's the one that cracked open NTT.