Doubt you'll find a lot of first hand comment. I see kei cars around west mich occasionally in the micro van form, is is veeeeeery cool. Stepped up to one in a grocery store pkng lot once and the guy gave me a tour of it.
Read up on the history of the concept. Its interesting. A consortium of SE asian governments arrived at a standard format for densly populated urban use to include delivery and transportarion etc, based on a prescribed wheel base and no-greater-than X in length width height.
The one above reminds me quite a bit of a bianchini (not a 'kei' car but about the same size) that our family owned in Rome, It. in 1965.
Our family also owned one of the first honda civics in 1972. 600cc air cooled twin up front. Under the hood it looked like some shop rat had just xplanted it from a bike.
For six years it took us in threes and fours all over west michigan. And that was back when highway speeds were even higher than today!
I seem to recall that small and underpowered was hella fun really!! (edited)