The Greatest Hero/Knight

In a magical world where you can find monsters who bring chaos and fear to humans, there's a hero not far away. The story is about Zane the hero of his people who defeated countless monsters alongside his trusted friends Ethan, Amanda, and Cale. Living a dream-like life with his friends, family (such as his brother Harry), and lover Jack. One day the life he treasures so much starts to crumble when he slays a monster which for a second becomes human in his eyes. And this would be hppening more often after that. At some point, he'd not only see humans in the monsters but also monsters in the humans.