Step 1: Climb the tallest mountain in Japan. Step 2: Bring a camera.
In all seriousness, this is a long exposure. It requires the camera to be stationary for a few seconds. In this case I used a 25 second exposure.
The best way to do this is to use a tripod, but carrying a tripod up 2000m of mountain trail is no fun, so I just placed my camera on some rocks and balanced it so that it was pointing down a bit. Then I help onto the strap in case it fell, but didn't touch the camera itself in order to avoid vibrations.
A useful trick is to use the timer delay, set to 2 or 5 seconds. This way, when you push the shutter release, the camera will wait for a few seconds before taking the photo. This will ensure that you do not shake the camera, resulting in a very crisp shot.
I'm sorry if that explanation was too rudimentary and you already know some of this stuff. I'm just happy to teach anyone anything I already know.