The world starts sliding into place the way it's supposed to a little more, and Castiel sighs a little in bliss as he tilts his head into the carress, holding out his hands. The belt is just another layer of ownership and security, love and care. He doesn't break eye contact with Sam as his hands are being bound, freedom of movement limited severely. But it doesn't feel like restriction to Castiel. It feels like security, care, love. Being tied up places him in the care of Sam, and Sam alone. It relieves him of the burden of choice, responsibility. All he has to do is follow Sam's directions, allow himself to be handled by that voice, and submit his free will by choice instead of design.

Already, he feels another layer of calm spreading over his frayed nerves.

"A little tighter, please," he murmurs, voice already going soft in ways it only does when he's at his most vulnerable with Sam. His eyes crinkle slightly at the corners. "Human."

It's a callback to their private joke. Sam had taken to calling him angel very quickly. At first, this had slightly perturbed Castiel - first of all, he was no longer an angel, and second of all he didn't understand why Sam would use his species as a pet name. He'd referred to Sam as human, then, and taken some delight in the heartfelt laughter it had provoked. To this day, he had no pet name for Sam, the weight of his name holding enough affection and desire to be recognized. But occasionally, he prodded at Sam gently with this.