I played through the championship in this game and came in first on every track up through Hawaii, but then it just gave me a trophy and dumped me back to the menu. What about the last two tracks? Do I have to do something else to unlock them?

Full track list require hardest difficulty.

Ah, of course. Should have thought of that, but I almost forgot there were difficulty settings, since they're not part of the race/championship selection process like in most racing games I've played.

I know it may not be an exact answer, but for those who just want to try locked tracks, there is a cheat code to be used in main menu – just type "refinery" and it allows you to play a race in all tracks (even if they still look like locked). Good luck with Tokyo in this kind of graphic quality xD