Jamie Peterson:

The first one was the "Madhouse AZ-1", which stuck to the kei limits - no widebody, 660cc. That's the one that set the 237.71km/h top speed in 1996. Before they set that record though, they realised the narrow track was pretty limiting on circuits, so they started the Cara R project (the first photos are from September 1995).

Ironically, the Cara R isn't based on a Cara, but a crashed AZ-1. They cut off the front and back to leave the central monocoque, then made tubular front and rear with double wishbones. The engine is still an F6A, but it's mounted longitudinally, and bored out to 720cc. They managed to package it without changing the wheelbase.

I assumed - and I know I'm not alone - that they were the same car, just developed further. But it seems the old car was kept as well, and when they remodelled the front of the Cara R some time between 1995 and 1999 into what it is now, it seems they also made similar styling changes to its little kei sister. It was Mad Usagi's ("Mad Rabbit") own personal car - I guess he kept it to be a road legal version of the race car.

In 2019, the little road legal car was spotted by Chibimal SV in a pretty decrepit state, with moss growing on it. The last photos I can find for the cars in running state are 2014 for the road legal "Madhouse AZ-1", and 2013 for the Cara R. Mad Usagi would be pretty old now, so that might be why they're no longer being driven.