We Are The Hunted

Kain. The normal boy who hunts with his father and lives in a fairly average village. These creatures that he hunts are giant masses of black who terrorize the village, city, and anywhere else they can reach. Using an old fashioned shot gun, and wearing his gas mask to block out the smog, he is just trying to impress his dad.
Valora. What Kain is actually hunting. A human hybrid. Her kind and many others have been hunted by the gas breathers and she is only trying to survive. All odds are against her, until she meets one of the gas breathers in person.
This is the part where I say that everything changes for the two, and it does. Dramatically.