How?

Moreover, the two association still have a lot of power after the earthquake happened. 

They should have been prepared in some ways.

Riya didn't know the details but she believed that they should have known that the world was changing very quickly, presumably after the mist suddenly appeared at that time. And it was because of this that the Martial Arts Association could still become a powerful association right now. 

Back to the point… 

"Because if you can't kill these magic beasts," Riya continued in a low voice, "You will always live in fear that these magic beasts will come knocking on your door and kill you. No matter how much resources you have, once the magic beasts came looking for you, it would be of no use."

Gun?

Gun could kill the unranked magic beasts and also the rank 1 magic beast.

But rank 2 and above?