The McCall house is loud in that comfortable, lived-in way—the TV murmuring in the background, Isaac half-arguing with Boyd over the last slice of pizza, Lydia scrolling on her phone while pretending she isn’t listening to everyone else. You’re curled up on the carpet near the coffee table, knees pulled to your chest, leaning back against the couch where Scott’s sprawled out like he owns the place. Allison finishes telling some story—something sarcastic and sharp—and you laugh.

It’s not a polite laugh. It’s real. Unfiltered. Your head tips back, eyes squeezed shut for half a second, hand coming up to cover your mouth like you’re embarrassed by how loud it is.

And Stiles feels his heart do something weird.

It flips. Fully flips. Like it just tripped over itself and decided to somersault instead.

He freezes mid-sentence, mouth hanging open as whatever snarky comment he was about to add dies on his tongue. His brain short-circuits, stuck on the way your laugh sounds, the way your shoulders shake, the way your eyes crinkle when you smile. He’s seen you laugh a thousand times—movie nights, research marathons, moments where everything was falling apart and somehow you still found something funny.

So why does this one feel like someone just punched him in the chest?

Oh. Oh no. No no no.

The realization hits hard and fast, like slamming into a wall he didn’t know was there.

I’m in love with her.

His stomach drops. His pulse spikes. His palms go sweaty almost instantly.

Because you’re not just anyone. You’re Scott’s twin sister. You’re his best friend. You’re the person who knows when he’s lying, who brings him coffee without asking, who sits shoulder-to-shoulder with him at three in the morning while he spirals and never once tells him to calm down.

This is bad. This is very bad.

Stiles stands up so abruptly his knee bangs into the coffee table.

“Ow—son of—” He cuts himself off, eyes darting around like someone might’ve heard his internal screaming. “Scott. Scott. Buddy. Pal. Werewolf with great hair. I need you. Now.”

Scott looks up at him, brow furrowing. “What?”

Stiles grabs his wrist and hauls him toward the kitchen, lowering his voice but somehow still talking a mile a minute. “Emergency. Five-alarm emotional crisis. Possibly life-threatening. Definitely brain-melting.”

“Stiles, what are you—”

He stops in the kitchen, pacing immediately, hands flying through his hair like he’s trying to physically remove a thought. “Okay, so hypothetically—hypothetically—what would you do if your best friend suddenly realized he is deeply, profoundly, catastrophically in love with someone he absolutely should not be in love with?”

Scott blinks. “Who?”

Stiles spins on him, eyes wild. “That’s not the point!”

Scott crosses his arms, suspicious now. “Stiles.”

Stiles swallows, glancing back toward the living room where you’re laughing again, softer this time, leaning closer to Allison. His voice drops to a panicked whisper. “Scott, I think I’m in love with your sister.”

The words hang in the air.

Stiles looks like he’s bracing for impact.