A/N: This is a very small drabble I've been toying with for far longer than I care to admit. Perhaps eventually I'll work it into something longer. I'm still trying to get my feet wet with regards to writing fan fiction again (a couple years away from writing will do that), so I welcome any constructive feedback or critiques.
Sokka knew he shouldn't have looked. This time, his instincts had been right.
Of two things he was certain:
One, Katara and Zuko had become a little too chummy for his liking. It was one thing for Katara to finally trust Zuko, but never had she ever gone out of her way to be friendly before. She smiled graciously when Zuko served tea, making an effort to "appreciate the aroma and delicate balance of flavors", sounding just as awkward and scripted as Zuko did when repeating his uncle. Sokka would have rather sipped swamp water than Zuko's tea - even with the germs and occasional bits of algae. Katara normally hated jasmine tea... except when Zuko brewed it as a pale imitation of his uncle's; it was twice as bitter and only half as sweet, but somehow Katara drank without complaint (although Sokka didn't fail to notice, with a bit of a vindictive smirk, how she would bend some of the tea out of her cup when Zuko's back was turned).
Two, the two of them spent far more time together than they let on. The way he would smile secretively - the way her cheeks would become rosy almost immediately... there was a marked difference between an awkward flush, brought on by trust that still lay raw and unfamiliar, and a flush brought on by memories. Sokka knew Katara well enough to differentiate between the two; he hadn't failed to notice that Katara would almost imperceptively nibble on her lip as she flushed, the strange way her lips would quirk as she did so. People who flushed from discomfort never allowed eye contact to linger, let alone smolder. Zuko made a point of not touching her when he knew that Sokka was within eyesight, conscientious to the point of seeming unnatural, but the few seemingly innocuous touches that passed between the two of them were intentional. Sokka knew it by the way Katata's whole body seemed to lean into Zuko's faintest touch.
He heard, rather than saw, the two of them sneak away when the moon had disappeared from the sky; their shadows melting indistinguishably into those cast by trees and rocks. The inky darkness failed to obscure their hurried footsteps: Zuko's even, heavy gait with Katara trotting lightly alongside him. Curiosity overriding the indescribable sense of dread creeping up, he followed after them, step by step -
He can't look. He doesn't want to look, and yet the simmering rage inside of him urges him onward.
Something rustles in the brush, and he can hear Katara giggling - the same kind of giggle she would have made were someone to tickle her... he thinks, except the unmistakable huskiness in her voice is oddly familiar. Listening carefully (wondering why he's only hearing one voice), he realizes it's the same kind of drop in pitch that he would expect from Suki when they would sneak away for a few moments and -
Oh. Oh.
For a moment, all grows quiet except for a barely imperceptible whimper that he knows is Katara's.
The pieces fall into place, and even while his thoughts grind to a halt, he can still hear the shuffle of cloth being moved aside, the rustle of the grass shifting beneath what he can image are two bodies unmistakably close to one another, and the quiet purr of Katara's voice, knowing that she's whispering something meant only for Zuko's ears.
Judging by the pitch of her sighs, Sokka knows that Zuko has done this before. He's not sure whether the thought sickens or enrages him. Sokka has spent enough time around Suki to know when the discomfort of unfamiliar flesh is replaced by ravenous curiosity to experiment with it, and the sounds Zuko has drawn out of Katara seem far too well-practiced to be merely from good luck. He knows precisely what he's doing, and Katara knows exactly how to encourage him.
Sokka fights the urge to hurl his boomerang at the pale-skinned boy; having had his suspicions confirmed, he returns to their camping grounds as quickly as silence allows.
A pot of jasmine tea, tendrils of steam still dancing around the rim, waits for him when he returns. Sokka steals a cup, confirming that of all the things that Zuko can apparently do well, brewing tea will never be one of them.
For some reason, the thought of Zuko being deficient calms him.