Comment by bamboozled

It's "kei" not key:

Kei car is the smallest category of Japanese, expressway-legal motor vehicles. 'Kei' is diminutive for kei-jidōsha, (kanji: 軽自動車), "light automobile" or "compact automobile" (pronounced [keːdʑidoːɕa]).

https://en.wikipedia.org/wiki/Kei_car#Description