When you name your car after a KS character. My Chevy Metro is named Suzu for two reasons. One, because it's got a Suzuki engine; and two, on cold days, it has trouble waking up.
When you give serious thought to what kind of cars the characters would own, despite the fact that at least three of them will never be able to drive.
In no particular order, here's what I figure:
Misha: A Harley-Davidson. It just seems to fit. And Harleys are known for their distinctive noise, after all.
Hanako: Also a motorcycle, but something more along the lines of a Kawasaki. A crotch-rocket, in other words. And of course, she'd wear the kind of helmet that completely conceals the face.
Shizune: A BMW Z4 roadster
, or something similarly powerful, expensive, and well-engineered.
Emi: A Mazda Miata
Rin: A VW Beetle, either old or new. Which she would be constantly forgetting to maintain.
Kenji: A Volvo station wagon, festooned with political bumper stickers.
Lilly: Something comfortable and reliable, but not showy or flashy. Maybe a Mercedes or Lexus.
Hisao: Actually, I could see Hisao relying on public transport or his own two feet for the rest of his life.
Mutou: A beat-up, but still well-maintained, old Toyota Corolla hatchback
Miki: Something fast and expensive. Corvette or somesuch. Or a
Meiko: Well, she's just this side of a soccer mom, so - minivan.