This kind of got away from the original prompt (Delena from Stefan's point of view) that PurpleStrawberryDreams gave me, but it also nearly doubled in size when I added in Katherine. Enjoy.
Disclaimer: I own nothing.
Pairings: Damon/Elena and Stefan/Katherine.
Stefan knows what's going on. He can smell Damon on Elena all the time now- on her clothes, her hair, her skin.
He sees how their eyes follow each other, how they have no personal space when it comes to the other.
He's surprised when he realizes that part of him expected this to happen. Those who don't learn from history are doomed to repeat it.
He knows they both know that he knows what's going on. Stefan can see it in how Elena doesn't look him in the eye anymore, and hear it in Damon's voice when he banters with Elena.
Katherine still pops up occasionally, even though she was supposed to never come back to Mystic Falls.
"You know, don't you?" she asks.
He drops the drained rabbit he's holding and wipes the blood off his face. "What're you doing here, Katherine?"
She shrugs. He's shocked to realize that she looks oddly uncomfortable, almost awkward. Katherine doesn't do uncomfortable or awkward, just like she doesn't do vulnerable, or anything other than confident and poised. "Nostalgia."
He raises an eyebrow at her, but doesn't comment. It's as true as anything else in his world at the moment.
Although he does wonder how she learned about Damon and Elena's affair before he did.
Elena finally comes clean with him partway through senior year and he finds her asleep in Damon's bed when he gets back from a hunt.
Words that they've both been holding in for months are exchanged. They aren't pleasant ones.
The dust settles to reveal Damon with a few more bruises, a coldness that wouldn't settle between him and Elena, and a completely demolished living room.
Everything changes. Nothing ever stays the same, not forever.
He finds himself leaving town with Katherine after the Great Breakup (he even capitalizes it in his head after hearing Caroline say it that way when she hears about the fight) and going to London, Paris, Milan, Rio, Tokyo, Atlanta, Los Angeles, anywhere and everywhere except New York. Avoidance is easy when you had the world to hide in, he discovers.
Katherine just rolls her eyes when he mentions this. Then he remembers that she ran from Klaus for five hundred years before they finally managed to kill him last year.
Another hundred fifty-odd years go by before he runs into Damon and Elena again in London. Elena's picked up Damon's sharp tongue and his habit of wearing black; Damon's smiles seem more real, especially when they're aimed at Elena.
"Hello brother," Stefan says, hands stuffed in his pockets as he stands half in shadow, copying the first words Damon had said to him in Mystic Falls nearly two centuries ago now.
"Stefan," Damon replies. Elena says nothing at all, but mouths an apology at him when Damon isn't looking.
He ignores it. Just because he's nearly reached his four hundredth birthday by now doesn't mean that he wants to be mature all the time, especially not when comes to his ex-girlfriend and his brother.
He leaves to find Katherine after a few days of catching up; she's disappeared (again) for what she said was a few months.
It's been two years since the last time he saw her. He's starting to get worried, even though he's well aware that Katherine can take care of herself (she gets upset when he forgets and tries to treat her like a delicate flower most of the time. She only likes it when she feels like being contrary the way only Katherine can pull off); and with the twice-daily shuttles to the moon, there's a lot more ground to search than the first time this happened.