He was an assassin. He killed for a living. Sometimes he hated what he did. He was really a good person at heart, but when you grew up with everyone telling you what you would be when you grew up. Telling you how cruel you were… you tended to start to believe it. So he buried the little part of him that screamed for him to stop when he held the knife to his victim's jugular, the gun to their heads.
His teeth to their throats.
After he came back from any of these he would wander the corridors of their ancient castle, disappointed in him self for once again being to weak not to do it, not to give up their protection and love. He wandered through the damp, dusty hallways, and couldn't help but think they reminded him of his existence. Dull. Colorless. Lifeless. There was nothing for him any more. He couldn't die though. He had tried. Multiple times. He knew he had to get away from them, but how? They were all he knew. All he had known since they had changed. Since they had given him this dark 'gift'.
They had remade him after he changed. Taught him the ways of the killer. Every form of martial arts, sword fighting, dagger throwing, he was a master of. They had taught him how to get to know his victims before he slaughtered them, and now none of them even had a slight chance.
Neither would this one. He would learn her habits. Where she slept, ate, went to school, what she did in her free time. He would get close to her. He would do it all and never complain, because they told him this was how he was made to be, even though every time he drank a human's blood something inside him died a little and instead of feeling the pleasure the others did, all he could feel was disgust. For himself, the others, and anyone who would live like this. But he kept on. Tried to be 'normal'.
That is, until he actually met her. The only one he knew he would regret having to kill. The one who had taught him so much in the little time he spent with her. The one he would one day learn he was in love with. Until he met he couldn't help but think of himself as a monster. Someone who killed for pleasure, but she showed him otherwise. She showed him they were using him.
Then she showed him how to get back at them.
But now I am getting ahead of myself. After all, the best place to start a story is always at it's beginning…