"You need to tell me if I’m doing this right," says Castiel. He pants the words over the back of Sam’s neck. "I don’t want to hurt you."
He mouths over the knob that marks the top of Sam’s spine. It’s slow like the way he fucks Sam, and Sam hates it because it’s exactly everything that he doesn’t want. Sam picked Castiel because he was strong, because he could hold Sam down and fuck the freak right out of him, but instead he gets this — this gentleness, this softness — and every inch of him wants to curl up with how good it is.
Castiel’s version of gentleness isn’t pliable. He’s firm and strong like nothing else that Sam’s ever met, and it scares the shit out of him. But he holds Sam down like he’s nothing, like these weird powers won’t hurt him, like Sam could dream about Castiel dying in a million ways and never see the consequences. It’s amazing and thrilling and awful because Castiel’s worried about hurting Sam when it’s Sam with the prophetic death dreams and the spontaneous telekinesis, yet Castiel covers him and holds him and fucks him until he’s shivering and moaning.
It’s all that Sam can do to just grip the sheets and go along for the ride — each thrust forcing his pleasure and each withdraw dragging out the want from inside him. There’s a peace to their joining that’s dizzying, that shakes Sam right down to his bones, and Castiel touches him as if he knows Sam, atom to atom — from the frequently cramping thigh to the instinctive guarding of the arm he broke as a child.
The easy vulnerability terrifies Sam, yet when he replies to Castiel on a stuttering breath — “You couldn’t… couldn’t hurt me,” — he means it. He believes it. Sam doesn’t know why Castiel reacts the way he does, not the suddenly painful squeeze of his fingers around Sam’s wrists or the catch of his teeth at Sam’s nape — only that it is finally what he wanted.