Erik skims a hand down the length of Charles' spine with a gentleness Charles will recognize, occurring in context as it does, and watches Charles settle on his skin with a half-lidded cast also recognizable, in context. He likes watching, a thing also not necessarily salacious, just present.
On which note: "Yes." His vocalization isn't exactly clipped, but it's certainly more minimal than the question it answers. He's noticed (only of very recently) that when Charles is very tired or very stressed he seems to project--flashes without intending to, no words or distinct images, only feelings. It had been recent because it had taken Erik that long to learn how to read him; Charles didn't share when he wasn't feeling his thousand watts of radiating chipperness out of much internal stoicism, it was just that it didn't matter. There were things that had to be done anyway. So he has some sense of Charles' loneliness and indefinable sadness, only the former offering him the easy solution of the comfort of his body.
He tucks Charles closer and idly adjusts blankets until they meet his standards of security, which is sort of like turning them into a fortress, and rests his head on the top of Charles', touching faintly cool fingertips to his bruises like he's drawing constellations out of them. "Do you want to sleep?"
Again, it's not ...purely salacious, at least not on its own.