You could either relate on pure skill or use the Hilde trick to get rid of your opponents.
The trick is to use Hilde and throw your opponents out of the ring. The cool thing is that the move is linked to the L2 button making it easier to pull off. At the beginning of every round just put yourself at the edge of the ring, guard to avoid being push out, when you see an opening press L2 and let the magic happen.
Select the Asian route as it has more opened arenas.
There is two difficult parts :
1 - The second fight takes place in a closed arena. Since you can't rely on ring outs this can be a frustrating fight. However, even sucking hard at this game I didn't have much trouble here since Hilde is a really good character.
2 - The final fight against Kilik. This is where I almost broke my controller. Some people on various forum claimed to have beatean the whole route in less than 20 minutes using this method. Kilik alone took me 50minutes game time. I guess it was bad luck. Just be patient and keep pushing.
Completing the route it will also net you this trophy :
Here's a video from Achievement Hunter showing the trick (credit to them for the trick) :