Look, he doesn't know when it started, ok. He doesn't know, he doesn't know. It's like one of those things where it feels like it just happened, but also like maybe it was always there.
He remembers the first time he saw him. He remembers that he had a lot on his plate at the time and that really, Cas's existence was just one more thing on top of a lot of other things, but he remembers thinking that there was something about the way he looked. Something about his eyes maybe, or his hair, or the expression on his face, a look at was somehow blank, and expressive, at the same time.
Dean has never been able to figure him out since. This he knows. Not that he ever actually decided to try to figure Cas out - certainly, he doesn't remember ever thinking "I wish I understood him." But he started trying to figure him out without realizing it. And getting nowhere.
Sometimes Cas looks at him like Dean means something to him. Which, obviously he does. But sometimes Cas looks at him like it's far, far more than that. And Dean starts to think that maybe he should be careful around Cas. Careful not to imply anything. Careful not to encourage him.
But then other times... Other times there's nothing to make him think that at all. Other times, Cas will even disappear for a long time, without saying a word, and then reappear with the exact same blank expression he had when he left, like the fact that he was away for so long means nothing. So Dean thinks: maybe he's right. Maybe it doesn't mean anything.
And part of him believes that. Like really believes that. So he doesn't know when it started. He doesn't know when, or how, or why, he started feeling the way he does now.
Dean is good at compartmentalization. He does his job when it's time to do his job, and when it's time to do his job he doesn't think about anything else. And then the rest of the time, he's pretty good at forgetting stuff when he's decided there's no use thinking about it anymore. Well - maybe not forgetting. Maybe just putting it out of his mind.
When he decided that the way Cas looked at him probably wasn't something to worry about, he put it out of his mind. He didn't think about it. He didn't think about it, and then he didn't think about it some more.
Until he woke up this morning and couldn't think about anything else. Couldn't get Cas out of his mind. Couldn't - couldn't stop thinking about Cas's stubble, about the lines under his eyes, and about his, his hands, his fucking hands. Dean suddenly couldn't stop wondering where Cas was, when he'd show up again, what he would say. Whether he would give Dean one of those blank looks, or one of those looks that make him feel like maybe Cas thinks about Dean all the time too. It's a nuisance.
Or is it, though? Is this a nuisance? Dean can't help thinking that this is just a temporary thing, a moment he's going through. Like when he was a teenager and sometimes he'd spend an entire day missing his mom so hard it hurt. More often than not, he'd wake up the next day and feel just fine. Just fine. So maybe that's what this is. A passing... thing. A passing hormone thing. A thing he needs to sleep on, so that his brain'll process it and file it away, so he can have some peace.
He doesn't know when it started. He knows that today it got weird but it started before, it must have. Things like this don't just go from zero to, to whatever this is, without anything in between. They build up.
But build up since when? Fuck, he doesn't know. Maybe it was always there, waiting somewhere in the background. Stalking him, waiting for him to let his guard down, like some weird power his sigil doesn't protect him against.
He wants - he just wants Cas to be here. He wants Cas to do that personal space thing. He wants Cas to look at him, to talk to him. He wants Cas to say "Dean" that way he does.
Does Cas know about feelings like the ones Dean is having right now? Of course he knows, he's been here long enough. But does he... Does he know? Could he know?
Could he know how hard Dean wishes he was here right now? How hard Dean wishes he could just turn around and see him? Just see him. It wouldn't fix anything, Dean thinks, it wouldn't change anything, it would just... but almost as soon as he thinks that he knows he's lying to himself. If Cas was here now, if he appeared right here in front Dean and said "hello, Dean," it would change something.
Dean takes a deep breath. Maybe that's what this is about. Maybe it's time for him to acknowledge this to himself. It's time for him to stop avoiding the actual words. "Yeah." He tells the air in his hotel room. "Ok." He squeezes his eyes shut. "I... I want -"