Throughout the ages, there have been many defenders to the many horrors that exist in this world. Horrors, both dark and evil. Horrors like the vile undead, the wicked demons, chaotic beasts, and filthy abominations. Yes, these things exist. The reason you don't know about them, is because of the defenders. Defenders like righteous paladins, purist monks, valiant slayers, and orderly banishers.
But these defenders are few, and with the world's growing population, are having a harder time protecting humans from the dark creatures. They've had to improvise to keep the order alive. In fact, most of the defenders are gifted youths in high school. These youths are in groups, and protect their areas, which often encompass an entire city. But still, with so many humans, contact is inevitable.
And thus, with assorted strange events, hybrids were born. Half-ghosts, half-demons, and half-werewolves, just to name a few. Hybrids are a strange bunch, being that they have the choice to be evil or not. Some give in to their horrific nature, some nourish their human nature, and some embrace both sides of themselves.
At this current time, Defenders don't know about the Hybrids. When they first discover there's a horror in them, they'll probably attack. But when they discover there's human in them as well... who knows? Maybe they'll keep hunting, maybe they'll just hunt the wild ones, and maybe, just maybe, they'll look for the Hybrid's help.
Defenders made a promise not to hurt humans, and to slay horrors, but... What if the horrors are half human?