[Nyororin]

Yes, the roads are really narrow here. Main roads aren`t (at least not in Nagoya) but there will be small streets that are about the width of 1 and a half cars, which will be both ways. When another car comes, you have to find a spot to pull off at the side (usually people`s driveway or in front of a business or something) so that the other car can pass.

I think the cars here are considerably less wasteful of space than those in the US. There is plenty of room inside the car - some of them are really spacious - just not a ton of extra space that isn`t used most of the time anyway. Gas use is lower thanks to that.

Oh, and you do indeed have to have proof of a parking space with a kei. I don`t know about in the past, but you definitely need to now. Currently, taxes are just lower. This applies in the countryside also (Father in law had to make a map and detailed measurements proving that every single kei truck he had for the company had a secure place to park on the property)
I would personally never choose to own a kei - they don`t do so well going over mountains, which we often do - but they`re fairly popular as little about-town cars.