Lelouch does not love Shirley – he loves the idea of Shirley. She lives in a world where Charles di Britannia does not exist, where people are simply people, where if everyone just sat around a table and chatted away like friends, everything would turn out for the better. That is not to say that she is naïve, not really; it is that she has hope, not for Britannia's defeat or the Emperor's death but for humanity, and that is something he lost long ago.
She is like flowers, like spring, like the first few moments of a sunrise; beautiful and lovely, Shirley is the sort of girl who prompts admiration and blush-inducing compliments from old women walking in the street. She is calm, friendly, peaceful, an island of normality—of the way the world should be—in the tempest of humanity, and in many ways, exactly what he is fighting for.
Shirley Fenette is a fantasy, and one he's wanted desperately—not just for himself, but for Nunally and everyone he loves—for a very long time. But he is Lelouch vi Britannia, and the difference between wants and needs will get him killed one day. While he might want Shirley, or at least what she represents, he wants her in the way the soldier leaving to battle wants one final kiss. In the way the conqueror covets the neighbouring kingdom's princess even as he seeks to grind it into dust.
War demands sacrifice, and, in the end, she is a sacrifice he is willing to make. He may not make it consciously, he may not make it knowingly, but Shirley's fate was sealed the moment they met, the moment he decided to only call her friend and nothing more.
He might love the dream of her, and in another world he might have been able to love the whole of her, but when everything is laid onto the board, Shirley Fenette is simply not necessary, and when she bleeds out in his arms, there is a very small part of him that is thankful she died before he could break her heart.
Lelouch loves C.C. in the way lesser men love the stars; that undefinable, indescribable longing for what you can see, but never truly touch. She is beautiful like a painting; regal, austere, and heavenly lovely, but it is a loveliness he cannot feel, a beauty made all the more stunning by being forever one step out of reach.
He has her, once, one night lost in the endless campaign, and the next morning he wakes in his bed to find she's no longer there. It seems fitting. C.C. is not something for mortal men to possess, or even to covet – she is truth in a world of illusion, a constant constantly apart from the zero-sum game of his life, and she has forgotten how to pretend to be anything else. Or maybe she just no longer cares. The distinction hardly matters.
She is an ally, and she can never be anything more; he needs her, but he understands enough about the world to know he does not want her. He might admire the stars from afar, but he knows not to get too close, else their radiance will consume him utterly. To court C.C. would be to court not death, but oblivion; not just of the body, but of the heart, the mind, and the soul.
He has seen what happened to Mao, after all.
And so, they circle forever apart, a radius defined by love and loss, by death and desire, by want and need and everything in between. But in a way, it is also defined by fear; C.C. is the one enemy he would never be able to defeat. She will outlast him—outlast the rest of the world, perhaps—no matter what he does, a goddess playing amongst children because it amuses her to do so.
And that terrifies him.
Lelouch does not love Kallen. Not yet. But he can feel it building, a slow burn that feels a little like anger; it shudders with every shared glance, reaching and clawing through the subtle intimacy of hours spent as soldier and commander, of late-night talks all the way through to morning's light, of the unspoken understanding that Britannia has stolen things from both of them that they will never again regain.
He knows he shouldn't let it happen, knows he shouldn't want this and that he doesn't need it (he's always been good at lying to himself), but then she walks into the room. Crimson hair, long legs; she's curved like a striking dragon, and his gaze follows her in the way thunder does lightning.
But it's not just that she is flawlessly, devastatingly beautiful, not by any means; it is everything she is despite this. It's her anger, fast and furious like a sparking flame, her determination, her drive to fight and win or die trying but only if you're going down with me. She is his red right hand, his savagery given form, his wind-and-lightning executioner. His queen.
Kallen is fiercely intelligent—not the smartest woman he's ever met, but close—and she wields her mind like a razor on the battlefield, so sharp he wonders how long it'll be before she cuts herself. Sometimes she's like a child – no sense of danger and an overconfidence in her own invincibility, but in the end she's always the one making his enemies look like children. She is the inferno, the storm, death on bloodstained wings, and she is glorious.
When he sleeps, he dreams of different worlds; in some, he's still a prince, in others he never was, and in others again he's something else entirely. Kallen is in all of them, somehow, somewhere, just like C.C., Nunally, Suzaku and so many others. But the difference is that she doesn't feel right in them – dream-Kallen is inferior to the real version, missing that spark that so defines her, a bright splash of colour on the world's fading canvas.
Shirley is a dream, C.C. is a goddess, but Kallen is life – and that, he thinks, is what makes all the difference.
So, no, he does not love Kallen. Not yet.
But he will.
Author's Note: Well, it's been a while between drinks, hasn't it? Almost a year since I last wrote something for Code Geass. You can thank Tumblr for inspiring me to write this one, if you enjoyed it =P (I have an account now, consanguineous-cacophony, if anyone particular feels like following it - I promise I reblog at least vaguely interesting things, and occasionally various writing snippets of my own)
Anyway, consider this part of my answer to a question I've never been asked: why do you ship Kallen/Lelouch?
P.S. If you recognise the chapter title as being the name of a song, you have my deepest respect.