yea.. I couldn't do it.. I was planning on beating Riku in swords 99 times, which I did.. but it was SOOOO boring, I couldn't take another 99 races! Yea, so I only got to 20 races... best route I found, is the simplest route:
1. Jump off the platform into the water and run towards the stairs
2. Run up the stairs a jump off the edge right in front of you
3. Run through water, passing by the ship
4. Run up the slope and touch the star
5. Jump down from the platform and repeat steps 1-3 in reverse order
But, like I said, I couldn't do it bcause I was bored after beating him 99 times, and you don't even get the satisfaction of Sora saying, now the scores 150 to 0! because it stops at 100 T_T