Castiel is not okay. In Dean's life of ups and downs and running like hell away from monsters every waking second, he can't be sure of much else but his hands on the wheel and his wheels on the road, but this he's sure of. Cas came back a couple months after disappearing, seemingly fine but refusing to say anything about where he'd been, and Dean knows better than to press him for details.
That doesn't mean he doesn't worry. He worries constantly, always watching Cas while still trying to keep an eye on Sam. Sometimes Cas stares off into the distance dazed, and Dean always pulls him back by calling his name, but when Cas's eyes meet his they only look more lost.
Sometimes he thinks that maybe Cas will die anyway, after everything, despite him being here in the bunker with him, safe and anchored. Sometimes, when Cas clamps down on his ears and keens like a dying dog, Dean wonders if it wouldn't have been better had Cas never come back, if he'd just vanished and never shown up again and Dean never had to watch him falling apart under his fingertips.
It's when Cas starts seizing on the floor, when Dean crouches down and rolls him over and his hands fly over him like he doesn't know what to do, that he can finally make out what Cas has been muttering, because he's screaming it now. "Don't make me go back, I don't want to go back," he screeches, sounding like a child, and at first Dean thinks he means Purgatory. He thinks Cas is flashing back, remembering that bloody place, and he thinks this until Cas calls out, "I want to stay down here, please," and then he knows.
Dean never refers to Cas as an angel, not to be facetious, not introducing him to other people. It's like he doesn't want to remind him. When he finds Cas's feathers, he tucks them away in the trunk of the Impala. He lets Cas go on pretending to be human because Heaven hurts too much.
He makes burgers almost every day, but Cas never eats, and he repeats everything he says to Cas like maybe if he says it enough it'll get through to him. And yet, despite everything Dean's doing to try and help him, Cas is deteriorating. He gets nosebleeds, or blood dripping out of his eyes, but when Dean asks him about it Cas seems like he doesn't notice.
Dean is inexplicably reminded of the fallen Cas he'd met in an almost-dream once, the one from 2014, except that Cas was carefree and this one cares too much. This one has nightmares though he doesn't sleep, screams in silence, gets claustrophobic from looking at the sky for too long. He feels safest in Dean's room, huddled against the wall or perched on the bed, but eventually he doesn't feel safe anywhere.
He's paranoid, Dean thinks, or maybe just plain crazy, and against all logic he keeps getting weaker and weaker, no matter what Dean tries to get him to eat. He rarely talks anymore, and when he does it's garbled nonsense and broken pleas to "stay, please let me stay". Dean's siphoning his time between watching over Sam and watching over Cas, and he laughs a little manically one day when he remembers that this place used to make him happy.
One time while Dean's on the phone with Garth, he glances over to see Cas writhing in his bed, and he hangs up faster than he can say goodbye and runs over to him. "Dean," says Cas, and with a jolt Dean realizes it's the first time he's heard Cas say his name in a long time. Now it's not really an acknowledgement but another plea as his searching eyes grip Dean's worried face in view.
"I'm here, I'm here," he says, head and heart pounding because no matter how many seizures- or whatever they are- Cas endures, he never adjusts to them. Dean's hands pin Cas's arms to the bed so he can't hurt himself and he hears himself cooing like a worried mother even as he kneels down at eye level with Cas. "You're here, you're home, everything's okay."
"Okay?" repeats Cas like word is foreign to him.
"Yeah," says Dean, "okay, Cas," and something in the way he looks down at the limp and shattered man on the bed reminds them both of the first time they met- the first time on Earth, in the barn where Dean stabbed Cas in the chest that's now struggling to contain him.
"You used," says Cas around a trickle of blood crawling out of the corner of his mouth, "to call me Castiel." And he doesn't say anything after that- Dean thinks he's probably not lucid anymore. He wraps a hand around Cas's and runs circles into the palm with his fingers, trying everything he can to hold Cas here, to let him know he can stay, he can stay.
Dean wants him to stay. Dean wants a lot- he wants Sam to get old, he wants Cas to get better, he wants a family and a house and for his world to get a whole lot less bloody. More than anything, he wants the pressure of Cas's hand on his to never go away, but you can't always get what you want.