I knew one Japanese guy with two cars. One Kei, for driving the hood, and daily commute. And one proper, large car for "showing off" in the big city. He said such was rather common.
The fancier is the car, the less people drive it so they can sell it at higher value.
I think part of the reason that people will have one Kei (or 5 number) car and one 3 number car is that there are a lot of narrow streets, tight corners, and parking spaces that 3 number cars will barely manage that are much easier to navigate with a smaller vehicle.
The fancier is the car, the less people drive it so they can sell it at higher value.