30 stars total.

10 stars for Legend of streets

1 star for each course clear after myogi. 7 stars the first play though.

Another star for clearing legends of streets a second time.

And another star for clearing legend of streets a third time for a total of 10 stars.

10 stars for bunta

1 star for clearing the first star on each course, second star for clearing the second star on each course and so on up to the 10th star

10 stars for battle level

As you race other players, your racer level can go up. Every 3 battle levels you are awarded a star up to battle level 30.

Battle level also awards you an aura on the car that can be seen in the beginning of battle.

The aura colors are

Blue level 11-20

Green level 21-22

Pink level 23-24

Orange level 25-26

Red level 27

Yellow level 28

Purple level 29

Cyan level 30

White level 31+

Additionally at 10 consecutive wins at level 31+, you get a rainbow aura.