While I've only seen a handful of them during my time in Japan, stories of encounters with these things abound. Can even find a number of people asking in Japanese about how to deal with them (I love how one of the answers lists the possibility of spraying fire at them). Their bites are rarely if ever fatal, but reports do indicate they are painful and can take a few days to heal. If they are common in your area, take care when putting on shoes and getting into bed!
I encountered one in my house for the first time last night. In my shower. Trying to keep me on my toes, I see. Nice one, Japan. The bugger looked kind of like this:
Actually it wasn't really that big; maybe about one and a half times as long and half as thick as my index finger. Still, was a little freaky to notice something crawling along the wall as I washed. In retrospect I wish I had taken a picture, but my first instinct was to kill it. So I quickly grabbed some tile cleaner and sprayed it good, but it was still moving. I had to bring out the big guns - Kabi Killer, which is actually intended for mold but also works on insects.
After it stopped twitching, I used a plunger to stuff it down the shower drain. That's what happens to centipedes in this neck of the woods. I wonder if I should be concerned about the return of the cockroaches, though...have never seen a centipede in my house before and they do feed on roaches. Hmmm.
If you're reading this, successor, be wary.