Although Lucius kept his cool façade even after Narcissa had broken the kiss, he felt himself drawn in to what she had been saying. For the most part, he'd taken it all as a game without any real goals nor foreseeable consequences. And then she had to go and say what she did, which suddenly made this more real than it had been. Not that Lucius wasn't expecting her to open up after he'd subtly invaded her mind, but perhaps he was hoping that she would take a different angle and just give in to his wiles, not pour out her emotions. Lucius didn't do emotions.
"It means," he began, voice low and hands covering hers on his chest, thumbs running ever so lightly against hers while he smiled slowly, passing his tongue over his lips to catch the flavour of her, "that you have obvious feelings for me, which may complicate matters." The coldness within himself was shining through, although he didn't want to simply leave it at that; he wanted to leave himself an opening for later, should he wish to revisit the possibilities with Narcissa. She was certainly an eligible witch for his plans, after all. All emotional attachments were pushed aside to a part of his mind that he forced himself not to visit.
"That is not to say that I don't appreciate your feelings, Narcissa; please do not mistake me. Given the general atmosphere around the school and outside of Hogwarts walls, surely you can understand how things will have to proceed at a slower pace." It wasn't a question, merely a statement which Lucius took to be fact. He tried to inject a bit of warmth to his words beneath the drawl, hoping that he was playing a convincing role.