Derek would never be able to understand why Stiles had been single throughout the entirety of his high school career. If they had been the same age and Derek had been in school with him, he wouldn't have been able to take his eyes off of Stiles as he moved through the hallways, laughing with Scott or arguing with Jackson. He was convinced that he would have spent every single day asking Stiles to go out with him like some lost, love-sick puppy until Stiles agreed.
Stiles knows he would have said yes the very first time.
Derek is enthralled by Stiles. The way he moves his long limbs like he has too much energy and can't contain it (which, he supposes, does make sense). The angle of his jaw and the obscene way his mouth hangs open at all times. Derek is absolutely certain that Stiles has the most expressive face he has ever encountered. It makes him wonder why Stiles even tries to lie because he is just so very bad at it. That's how it all starts. Derek catching Stiles in a lie.
"You know you can't lie to me, right?"
"I-I...don't know what you're talking about."
"Stiles, I can hear your heartbeat. Right now? You are lying to me."
It's an unusual start but it's in that moment, with Stiles floundering for an excuse and Derek scowling at him, that Derek realizes maybe he doesn't dislike the kid. Maybe he actually kind of likes him. And maybe he really wants to kiss him.
Their first kiss happens so quickly that Derek isn't even sure it counts. Stiles tells him it does but he's still not convinced. It was just a slight press of lips in the middle of an argument ("Fight, we were definitely fighting") and it was all Stiles. Derek didn't even have time to kiss him back.
The first time they make love (Stiles calls it that, not Derek), Derek spends so long mapping out every inch of Stiles' pale and freckled flesh that Stiles almost orgasms the very instant that Derek thrusts into him. They last roughly six minutes before Stiles' mouth falls open, tongue pressed against the roof of his mouth and Derek's rhythm becomes erratic. Derek wants to squeeze his eyes shut because the force of what he's feeling is so overwhelming but he can't. He can't stop looking at Stiles because he's just realized that he's in love with this hyperactive, compulsive lying little shit.
The next day is the first time they hold hands. Stiles is adamant that this should have come before the sex ("I thought we made love" – "Oh shut up, Derek") but Derek really doesn't care. He laces his fingers with Stiles' and maybe he even smiles a little at his betas as they come for the pack meeting.