Because of the amount of guilt and pain he has endured, be blames himself, and he doesn't trust anyone in town. But while he claims to be greatly annoyed by Cecilly, he often finds himself swayed by her. He even buys clothes for his demon, Lisa, because Cecilly made the strong suggestion.
Luke will work for money, but has a strong conscience and will not waver from his morals. And while he rarely sees eye to eye with anyone, he gets along probably best with Aria (Cecilly's sword) and his demon Lisa. This isn't to say though that he doesn't secretly have feelings for someone else. Cecilly was brought very close to rape on account of the traitor, Siegfried, but refused to tell Luke. In fact, she was the last person that she wanted to tell. So once she recovered from the experience, she came to the realization that she would be the only one to save herself. She challenged her attacker and was about to be deeply disrespected by Siegfried again when Luke showed up. Apparently, he was filled in by Aria about what had happened between Cecilly and Siegfried and challenged him to a duel, making a bet that he would never touch her again if he won. And so they fought, trying to kill each other. The battle was a complete bloodbath. Luke lost his bad eye entirely and by the time they were stopped, they were both bleeding from head to toe. The result left him saying things to Cecilly that he would never normally say--like asking her to dance.
While Luke pretends not to care about anything, what he does care about, he protects and fights for with his life in his hands. He hardly ever does anything half-heartedly. And while it takes forever for him to get fired up, eventually his emotions will overcome his ego. If Luke continues to move forward, it will be likely that he can not only leave the memory of the original dead Lisa behind, but he will fall completely in love with Cecilly.