Warnings: Rated M because of male/male incestuous relationship and suggestive content.

Author's Notes: Written in response to a CLAMPkink prompt requesting "Fai/Yuui. Intercrural sex, oral."

He only means to give Yuui a short, sweet, simple peck on the cheek. Really, truly, only. But Yuui chooses that moment to look back over his shoulder to say goodnight to the brother who'd jumped into his bed still damp from the shower and glomped him like they were still tots instead of teens, and it all falls apart. Instead of a smooth cheek, Fai's mouth makes contact with lightly chapped lips. He smells toothpaste and tastes mint and feels his heart stop because instead of laughing at the fumble like he should and chasing after the cheek-kiss he'd originally been after, Fai makes three mistakes back to back.

He lingers for just a moment too long, caught up in warmth and sweetness then realizes his first mistake and goes right into the next, which is to flinch back with his eyes wide and breath caught. He might be able to gloss over the first two mistakes if he laughs then. Better late than never. But he makes mistake number three by opting for "never" instead of "late" and just stares.

Yuui stares back.

The not-breathing and not-moving and not-blinking stretches out until Fai's eyeballs finally began to sting and he blinks a couple of times in rapid succession, and for some reason that makes Yuui draw in a deep breath as if he's just remembered that breathing is a good and necessary thing. Yuui presses his lips together and then opens them again, and out of a sudden fear of what his brother might say to end or minimize the moment Fai quickly leans in to silence his twin with another kiss.

He's not sure people can actually kiss another person silly, but he definitely manages to kiss Yuui incoherent. Even after he releases his twin's mouth, all Yuui manages are soft whimpers and an odd assortment of breathy noises. The younger has turned fully around so that they're facing each other, and Fai maps out the body he already knows by sight with his lips and teeth and tongue and it's like getting to know his other half all over again from zero. Yuui's earlobe is delightfully squishy, and his neck is more ticklish than Fai's ever known it to be, kicking up a storm of squirms. Yuui's wrists are unexpectedly sensitive, and Fai gets his hair yanked in a way that ought to hurt but doesn't. He's puzzled to find a tiny mole high on a hipbone that he didn't know about.

He has only a vague notion of how to give someone a proper blowjob, but on the other hand Yuui has no idea at all what a proper one is supposed to feel like. It seems that either Fai is a natural genius or Yuui is overwhelmed and overwrought and oversensitive because it can't be much more than a couple of minutes before Fai's hair is getting yanked again, but this time with a clearer message of stop. He doesn't want to, but is it impossible for Fai to knowingly hurt Yuui in any way and so he stops. But then again he's Fai and pretty well used to getting his own way, so he just stops for long enough to whisper up that he wants to and adds please. When he ducks his head again Yuui's fingers are still shaking but not tugging any longer.

Yuui is hot and salty against the back of his mouth and Fai chokes a bit, coughs and clears his throat and laughs for no real reason before crawling his way back up toward the warmth and sweetness of his twin's lips. Yuui is even more breathless and gasping than he is, so Fai contents himself with just snuggling close. For a few seconds, at least. Soon enough he's discovered that innocent snuggling is not an option when you're achingly hard and rubbing up against a smooth body wet with sweat and spit and slippery slickness.

Fai murmurs something, the noises meaningless and his voice rich with want, and the arm he isn't lying on is busy pulling Yuui closer. He rocks forward and slides his hand down and longingly tells his other half that he wants him and means it in so many ways. The hand cupping a smooth buttock and the insistent way his hips are working perhaps give the wrong impression, or at least just one impression out of many, and Yuui is trembling anew. The fingers in Fai's hair are shaking, Yuui is shaking his head, and even his voice is shaky.

"Can't...we can't..."

Fai is surprised, because he hadn't been asking for that. He hadn't thought about reasons before but he knows immediately why Yuui is saying no, and agrees with everything his twin isn't saying. Because they don't even know what they're doing, but they know enough to know that there'll be blood and pain and hurt if they go ahead and attempt it anyway. Because they might not be able to hide what they've done if they do it. They're not girls and blood doesn't belong in the middle of their sheets, and Yuui doesn't do the type of sports and stunts and stupid things that would leave him limping in quite that way. They might be found out, and they might be talked to, and they might be separated.

But they are boys and fully functional ones at that who've already had some embarrassing laundry to do, and so Fai doesn't let go and doesn't let up.

"I know," he soothes. He kisses. He clutches Yuui a little tighter and rocks his hips a little harder. "I didn't meant like that. Just hold me. I just want you." Yuui's lack of clarity earlier did not impede Fai's understanding and the reverse is now the same. The younger twin nods and then they squirm on the bed, trying to get both arms around each other despite gravity getting in the way. Yuui wriggles one limb free of his own body weight and throws his arms around Fai's shoulders, and a scoot and writhe makes Fai suddenly arch his back and gasp at the way it feels when at the next press forward he isn't just rubbing up against his twin but nudging and sliding between sweat-slippery thighs.

He could get more pressure and control by using his own hand but this is far, far better because it is Yuui. There have been girls aplenty and some boys, too, who he knows would have been willing to give him this heat and friction but he's always turned all of them down and away. Despite the physical connection there wouldn't have been any closeness. Despite the pleasure there wouldn't have been any joy. With Yuui there is the fear of condemnation but he's past caring so long as it doesn't come from Yuui. So long as Yuui loves him back, he will love Yuui all day and night and as he dreams, and he doesn't need understanding or approval from anyone except this other half of him.

Fai doesn't last much longer than Yuui did, and that feels right. They are identical and opposites, similar and strange, getting to the same place by different routes but holding hands the whole way. Fai leads and Yuui follows, but Fai only leads because Yuui is there to be led. If he didn't have Yuui, he wouldn't be Fai.

Fai shudders and gasps and smashes his face into in his twin's neck, clawing Yuui's scent into his lungs and licking up beads of perspiration with sloppy kisses. Yuui is sweet and pure and tangy and hot, and Fai thinks that he will never be able to get enough of this feeling...this lying here in warm wet darkness, sliding against each other in an awkward tangle of slippery limbs, devouring sweet kisses and lustful groans off of each other's lips. Now he finally knows what's been missing though it was there the whole time, what he's been aching for thought it's belonged to him all his life. He's stumbled into a taste of what ought to be forbidden fruit, but he is not just anyone; what is poison to the world is the only food he can live on. The first taste awakens an unending hunger, and he will never stop feasting, and he will never get enough.

Sugar and spice, and a hint of vice; that's what his soulmate tastes of.