Standing between demons dominating the entire continent lays a nation filled with fighters who pride themselves on keeping the evil at bay. Demon hunting is a lucrative and revered profession. 
Xellie wishes to become a hunter feared by demons, helping clean up the world. Motivated partly by wanting to save lives, partly by money, but mostly wanting to prove herself to her brother, Niko - a famous demon hunter partnered with an equally famous exorcist.
It's a simple mantra to live by. Demons are bad. People who summon demons are also bad. It can't be complicated, can it?