Hello!

I was looking for fast-paced FPS like Quake, and this is what I want! Except there's no player in Asia...
I'm happy to play such a good game for free with active community. 

Welcome to Xonotic! I think there are a few servers in Asia now, and there seems to be a few players from Asia from time to time. Try joining those low ping servers and see whether you can get other nearby players to join.
You can always invite your friends, too!