Parking on the roads in Tokyo are a pain in the left buttock. In most places you can park for only an hour - in this case its 300 yen. If you park for more than an hour, the side of the parking meters start to glow red making it easy for a traffic warden to spot from afar.
If you want to park for longer in the same spot, you need to move the car and re-park it. We discovered that there is some sort of infra red beam that hits the car when its parked. Unless the beam is broken, it thinks you are still parked. If you are lucky enough not to have anybody behind, you can just move the car back a bit to break the beam and then move back forward. Wondering if a deflecting mirror would do the trick instead? ^^;
The meters don't let you put in money to cover a few hours either. I'm presuming that they do this so that everybody gets some parking time.