spoilers; none whatsoever, although it's a Post-KH2 fic.
notes: also archived here and the original draft can be found at surestsmile.
Kairi has a lot to think these days. Whether she's making more thassala projects or chasing down Riku or bedding her two boys down in the small shed and watching over their nightmares, she thinks in deepening, widening circles, wandering forever around the same thoughts.
Riku will tear Sora apart, whether he's with him or without him. The proud, egotistic boy of old is gone, Riku is now a double-edged sword, sharp and black and bleeding from the mistakes he made when he was young. He loves Sora and he hates himself for loving Sora, and he hates that Sora loves him with a love so blind when all he wants is for Sora to love Kairi so that Sora will be safe from him because he loves Sora and he hates himself.
Kairi sees this. Sora doesn't, and because of that Sora doesn't understand, sweet simple Sora with the lion's heart and the child's mind and the hero's life. Sora, who believes that love and faith and trust (and pixie dust) is all you need to turn someone else around, no matter how deep the darkness goes. Sora won't hurt Riku and Sora doesn't see that his kindness is slowly killing his best friend.
So she hits Riku when Sora won't, when Sora runs up to her with lost eyes and babbles that Riku's gone (again) and they search for hours (again) before Riku re-appears without so much as a word (again), and she screams the entire town down in fury when she sees him (again). Her girly slaps don't do much except leave marks on Riku's fair skin (he doesn't try to shy away), and leave her own palms stinging red, but she can't make Riku leave, and she won't anyway, especially when Sora grabs her hands and says, "Stop it."
Riku is unrepentant however, and he simply looks silently away from her while she wipes messily at her angry, shameful tears until Sora finishes fishing for a dirty handkerchief, but she grabs the both of them by the wrist instead and drags them off from the prying eyes of the other islanders.
She can't make Riku leave, and she won't, because Sora needs him, needs him more than her and she knows that she can't fill in the gaping emptiness Riku had dug into Sora, those two years ago, Riku-sized and Riku-deep and she's only Kairi. But Riku's too broken to even think about fitting in and she tries, she tries so hard. Because she loves Sora, and she loves Riku, and she doesn't want either of them to be hurt.
Sora clings to the both of them, clings so tight that her hand cramps for hours later, as though if he doesn't hold them, if he gets careless they'll both fade away. Riku doesn't complain, and maybe he squeezes back with equal fervour because he can't trust his voice and his words anymore, but Kairi doesn't know, Kairi only guesses because Kairi can't read Riku anymore and Riku never, ever holds her hand. Kairi can't match Sora's strength so she allows him to hold her, but wishes she could tell him that she can hold him too, if only he'd let her try.
She makes plans of her own, secret plans, some silly, some serious. Plans like making a gummi ship (even though she doesn't even know where to begin in the first place), or taking the old raft and set sail, like what they had planned to do two years ago, or splitting the paopu three separate ways and squashing it into each other's mouths with their own. Plans like moving out of the mayor's home and making it on her own, or getting Riku and Sora and herself a place to call "ours", or actually finding a way to turn back time so that the past never happened.
But she knows that Riku and Sora will never forget the two years, they can't. And it's unfair, really, unfair to the worlds and the lives that they had saved and the hearts that they set free, but she wishes she could be a little bit more selfish and a little less Princess-of-Heart, but she knows she can't. She's locked into her role, locked and chained and so is Sora and so is Riku.
They can't escape.
She laughs bitterly that instead of forgetting the past, they have chosen to forget, or never bothered to remember, that the darkness is gone and life has become easier and that they didn't need to fight anymore. But Riku still rarely sleeps more than an hour when he does sleep and he always wakes with half a scream, green eyes alive only with mad fear and his Keyblade sings inside her heart, crying in the same way its master never could. Sora spoons around them when she manages to get them to nap and his muscles remain forever tight and tense, no matter how hard she pushes at them they never release, and sometimes she quietly teases that the both of them will get so horribly old before twenty-five.
Sora laughs too loudly while Riku looks at her with dead eyes, and she wonders if she cuts him he'll bleed Heartless black instead of red, but Sora balances Riku out with his anger and his sadness and his smiles and he overflows with emotion, and sometimes Kairi wonders if Sora would shudder out of his skin one day, burst like a butterfly.
They're almost always together nowadays, almost, sitting on their disused raft or sleeping in the shed with the door open to let the salty island breeze in or staring blankly into the distance, each one dreaming of something different and secret, and no one really bothers them except for Selphie, Wakka and Tidus, because they're still friends. Selphie's even taken to poke mildly at their closeness when she drags Kairi away to do 'girl' stuff, saying, "Yanno, maybe I should refer to you guys as RikuSoraKairi now," fast and fluid like they're stuck together as one and she surprises herself by laughing a little, because she wishes it could be true.
Because sometimes she watches the two of them, RikuSora without the Kairi, and she sees the perfect sum of light and dark without the unknown, unstable variable, and she closes her eyes and wonders why she should drive herself insane (or insane-er) with them when she should just let go and leave them be. And then she thinks about how Riku wants to let go and Sora won't let him, and she, she's the one who can and can't.
She's not a lover, she's not their lover and she knows she never will be. But she's a mother, a girl with two little boys to call her own, beautiful broken boys who live in a small, singular universe of two she knows she can't step into, not now, not any longer, but she'll watch over anyway, because it's all she has.