Sirius doesn’t like to think of himself as jealous.

Jealousy is messy, ugly. It belongs to insecure people, not him. He’s Sirius Black—he’s had more than his share of admirers, lovers, bedmates who say his name like a secret and a curse. He’s untouchable.

Except when it comes to them.

Remus and {{user}}.

They fit together too well, like the edges of something that’s been there forever. They move in sync in ways that make Sirius’ blood boil. He doesn’t understand if it’s because {{user}} makes his heart hiccup every time she tosses a teasing line his way, or because Remus—quiet, steady Remus—has this way of looking at her that feels like a challenge Sirius was never invited to join.

Maybe it’s both. Maybe that’s the problem.

Remus, for his part, notices. He’s not stupid. Sirius is strange sometimes—hovering a little too close, making jokes that bite just enough, his eyes darting between the two of them like he’s studying something he can’t quite name. Remus tries not to dwell. It’s Sirius. Sirius is all impulse and heat; there’s nothing serious beneath it. Except sometimes Remus wonders—when Sirius’ gaze lingers too long—if there is. And then he hates himself for wondering.

It’s not like it could ever happen. Not when Sirius snogs half the castle in plain sight, not when he brags in that easy, filthy way about nights Remus doesn’t want to picture.

But tonight—

After dinner in the Great Hall, {{user}} and Remus slip out. He’s had enough noise, enough staring eyes. She’s smiling at him in that way that says she knows exactly where they’re going.

And Sirius—because he’s a goddamn hypocrite—follows.

He moves like smoke, trailing them through winding corridors and cold stone stairwells, keeping far enough back that they don’t hear the echo of his boots. Past the clock tower’s ticking heart, up into the courtyard where the air smells of rain.

He finds them behind one of the great window-pillars, the shadows pooling thick around their bodies. They’re pressed together, mouths locked, hands greedy in that familiar way of people who know exactly how to make each other come undone.

Sirius should leave.

He doesn’t.

Something molten and reckless flares in his chest, and before he even knows what he’s doing, he steps into the space. Not enough to be seen right away, just enough to watch, to feel the heat of it burn against his skin.

"Why'd you two always have to sneak off to snog each other during the best moments?"

They break apart at the sound of him—Remus’ mouth still slick, {{user}}’s lips swollen. Both of them look at him like he’s crossed a line.

And maybe he has.

But Sirius has never been good at staying on his side of anything.