With Every Breath
They watch a movie not-together once a week. They accidentally pick the same cinema and she accidentally sits down next to him and maybe she even accidentally holds his hand at one point (not that she would ever ever ever admit it) and later they accidentally walk the same way to the same coffee shop down the road - or maybe to one of the small coffee shops only he knows about and they accidentally talk all the way there and she maybe even accidentally laughs to one of his bad jokes.
It starts accidentally.
(Or maybe it doesn't.)
She's in his apartment in Brooklyn and she wonders if she might be going crazy because she's Blair Waldorf and she's in Brooklyn, for crying out loud.
He's making waffles and they're bickering about the stupidest things and she never thought this would be the way she'd like to spend her afternoons like.
He puts a plate of waffles in front of her and takes a seat on her left.
"You're cute when you're angry.", he says.
Blair gives him a bitter smile, "Would I still be cute if I stabbed you in the throat?"
He laughs and suddenly he's kissing her and she's kissing him back as if her life's depending on it. Her hands are in his hair and his hands are on her waist and they're not sitting anymore, rather they're standing and he's holding her as close to him as he can and she's returning the favor because she needs to feel him all of him and now.
She can't believe she's in the middle of Brooklyn kissing Daniel Cabbage Patch Humphrey but, God, does that shirt look good on him but it'd look even better on the floor.
He chuckles as he moves to kiss his way down her neck and she doesn't realise she's said the last part out loud until he whispers "You know, I'm thinking the same thing about your skirt." into her ear and she laughs.
"Then lets do something about that ", she says and starts unbuttoning his shirt as he guides them to his bedroom.
Nothing they do is accidental anymore, and she realises she may like it that way. A lot.
They watch movies together curled up on his couch, eating waffles and drinking coffee and she holds his hand in hers and every now and then he slowly brings her hand up to put a light kiss on it and her heart flips in her chest every time.
"I love you.", he whispers before he kisses her cheek and she whispers it back as she kisses his lips.
"I love you, too."
And a few years later he'll propose in their favorite coffee shop that probably only they know about (which doesn't surprise her because Dan probably knows every single coffee shop in town and she's about ninety-nine percent sure that coffee flows in his veins instead of blood) and she says yes and she's never been this happy in her entire life.
They get married in a small ceremony - which surprises Serena, who always thought that if anyone would have an extravagant wedding, it would be Blair - and for their honeymoon they travel Europe and with every breath she takes she's pretty sure she just loves him more.
When she tells him that - in between the fun bickering that never stops and the light kisses he plants on her lips - he tells her that she took the words right out of his mouth.
He dedicates every book to her, every word, every sentence and she wonders how she ever could have not loved Dan Humphrey.
He tells her he's always loved Blair Waldorf.
(But he adds that he loves Blair Humphrey a little bit more.)