I've finally beaten Kaido Racer! I had to get all 40 prizes before Ground Zero would come out, and the lvl 10 CA battles in Aso were pretty tough...
Now I'm just messing about with the game, buying and tuning my favorite cars.

So there is 40 prizes in this game as well - like in Kaido Racer 2?

Yup, and they're not as easy to get as in Kaido Racer 2... you have to do advanced category races to get half of them.
(The other 20 are obtained by beating Medalists)
And you can't participate in them unless you have enough Entry Tickets. The daytime races are quite different from KR2 (TXR:D2).
It's sortof set up like the Gymkhana races in KR2. There are 10 levels and to reach a higher level you need to complete at least 3 out of 9 CA battles per level.
As you reach a higher level, you get more Entry Tickets. And for the Aso stage you need 70 tickets to participate in an advanced race, so you need to complete all 10 levels.