Her immediate response doesn't actually help Derek because the color in her cheeks contradicts that negative response word and Derek pauses, waiting. He should wait, right? Before he decides how to respond to her? Because right now, he's not really sure that he understands the "no" properly and if there's one thing Derek isn't, it's That Guy who takes no for a yes and does the thing anyway. So he waits.

When she goes on, the no becomes more clear with extra context and he smiles a little. Maybe it's his turn to blush a little bit, because he really did spring that on her and he hadn't meant to, it had just...felt like the thing to do at the moment and he'd put exactly no thought into it before, during, or after it. Now he kind of wishes he had because she clearly has.

"Are we not?" he asks and it isn't coy or worried, it's matter-of-fact. They're friends, sure, but he's friends with Buffy, too, and he doesn't sleep with her in his arms every night or kiss away her nightmares when they come. What he and Katniss are is absolutely something more than friends and probably always has been, whether either of them want to put an actual label on it or not. He knows this. She must also know this. They're just both gun shy when it comes to admitting it aloud, which is fair. It's entirely fair, really. "I guess it just feels like a natural progression even if we don't call it anything, I don't know," he admits.