After 10 years in Japan, I still haven't figured out the bullet trains.
First-class seats are in the "Green Car," although there is nothing green about it. If there were a few trees inside, or even some "o-bento" grass growing between the rows, I would understand. Then there are super express and limited express trains.
"Limited express" seems like an oxymoron to me. Or at the very least, a regular moron. Perhaps "limited express" refers to the train's limited ability to express itself: It's an introvert.