moped in Tokyo?

Hei all,
We are moving in August to Tokyo for 4 years. Instead of buying a car, I was thinking about a scooter. I have a norwegian drivers license allowing to drive a car here, so I guess obtaining a license in Japan will go ok.
But as I am totally unknown with habits and traffic there I wondered whether scooters are an ok way to move around in Tokyo. Is it allowed to have a passenger on the back of the scooter? (I am thinking vespa -size).