Cas is honest to a fault.
Except, of course, when he's not.
He tells Sam that he can't see Lucifer anymore, that the 'after taste' had faded (with his mind with his mind! all the choirs say, all the choirs say...), that there really isn't anything wrong. And there isn't, really, seeing all hearing all knowing all aside. (He wonders if this is what God is like - if God can tell him what it's like to see the path and be lost, to understand and be ignorant) He can see the weave of the universe in the things no one looks at - or the things no one sees - or the things no one dares to see. He can see the path of a bumble bee the moment it takes flight, around and around and around, lazy bubbling swooping lines. (He can see the lines in the sand that have been crossed out or crossed over, the lines people have drawn around themselves, the lines that draw one person to another, the lines that break them apart.) Most of him - the big parts, the great grand greedy dying parts - thinks and sees and knows, and that's all, that's everything, the long and short of it. He thinks and sees and knows, but opinions are lost in translation, taken by the wind, away away away. Or, they almost are - he won't fight. He won't ever, never again. He can't - because the greedy human hopeful helpful practical part of him swims under his skin, flat and benign and thin, for the moment, like the wavering image of a shark at sea, the shadow of a condor on the open plane. It floats and it sits and it taunts him, sometimes, in the night, when his vessel should be sleeping but he can't so it sits there and tells him tails of power and greatness and conquering.
This is how he knows Lucifer isn't gone.
This is what he does not tell Sam Winchester.
Sam isn't surprised when Cas visits, after everything is done.
It's a sad thought, but he knows the angel doesn't have very many places to go to where people won't attempt to commit him, or taunt him, or hurt him.
Sam thinks of him sometimes as a very intelligent, very tired, very hopeful dog. He doesn't think it to be mean - never, ever, not to Cas - but it's just about as close to the truth as he can rationalize, after everything he's said and done and seen. It's easier to think about than 'fallen angel who saved my sanity and attempted to take over the world but was on our side the entire time even though we got snarky and he sort of left us in the dust'. A lot of things are easier to think about than that.
So it doesn't surprise him much when Cas makes it a regularity to find them, wherever they are, and visit for days or weeks on end. He stays, he sleeps, he eats (but he doesn't really have to? Sam still doesn't get it entirely), he plays board games and watches cartoon reruns and stupid movies and celebrates with them, if theres a holiday. He gets better at cooking and gift giving and understanding that, no, you do not just teleport in on someone when they are in the shower, it's just not done.
He gets better and he gets worse, and that's the long and the short of it all in one.
He gets better, but they aren't trying to fix him. Does that make it worse?
Sam feels like that makes it worse.
So when Cas appears to him on quiet afternoon in their boonie-cabin on the skirt of the Montana-Canada state line, Sam really doesn't think anything of it. Dean is asleep, calm for once even though anxiety and nervousness still runs rampant through them (they've been part of what was making or breaking the world for too long for the feeling of anticipation to simply go away). He sprawls in an undignified heap on their ratty couch, flipping through ten tonnes of boring t.v. channels in his boxers and a wife-beater, because there's nothing to do and no one to see. He's just flipped to some sort of cake show (Top Chef? he can't be sure), when the familial sound of rustling paper greets him. He rolls his head back and, yes, there is Cas, standing just behind the couch and faintly damp. Wherever he was, it had probably started raining before he remembered to get out of the cold.
Sam doesn't say anything, and neither does Cas, although the angel does move around to the front of the couch, casually shucking his trench coat on a chair as he goes. His weight forces the couch to shift, moving Sam, before he falls onto his side with his head on the younger Winchester's thigh. He shifts, settles, adjusts his limbs into something comfortable, and then stills, eyes fixed on the panicked men and women bustling about on the screen. They don't seem to have enough time left to do what they need to do.
Sam remembers what that feels like. The smile that curls the corner of his mouth doesn't reach his eyes.
But no one's looking.
He absently reaches down to card his fingers through the other man's hair, long, sure strokes that start and end with a scratch of his nails against the skin of Cas' scalp. The angel shifts, sighs, settles into the touch. Three of his fingers twist into the hem of Sam's boxers. Sam sighs, scratches a patch of stubble with his other hand, and turns his gaze back toward the t.v.
Someone's getting voted off today, and he wants to know who because it feels like something to do.
It's awkward being content.