It has been a long time since I watched the series, but somehow I seem to remember C.C. kissing Lelouch near the end of the first season, I think, before some crucial battle. But maybe I'm just imagining that and remembering nonexistent things if DarthEnderX has got such a view of things.

All in all C.C. was the only person whom Lelouch could really trust throughout the whole story, who was more or less always with him, through fire and water. They really spent a lot of time together, and it wasn't any stiff business relationship. He tolerated her selfish, capricious behavior unlike anyone else's. I always felt like Lelouch had two bottom lines: Nunnally and C.C, the only difference being that C.C. didn't need a whole lot of protecting and was actually useful, but both of those two girls were the elements Lelouch needed to keep going, though for different reasons.

At the end of the day Lelouch probably requires a weird woman to keep him company. He's pretty weird himself.