"You know, in some cultures, people believed that freckles marked where you were killed in a previous life," Castiel said, closing his eyes as he laid down on Dean's stomach. He pressed a kiss onto the sliver of skin that was exposed under his t-shirt, a patch of flesh just below his belly button.
"Oh, really?" Dean asked, smiling. He hummed as Cas went higher, rolling up his shirt to explore more of him, lips finding the dips in his hipbones, mouthing promises into them in the pale sunlight.
"Yes," Castiel said, using his elbows to prop him up as he moved further up Dean's body. "Hmm. I'm going to say gunshot wound." A dark black birthmark dotted him just below his last rib. Cas kissed there, and then moved higher. "Stabbed with a knife, I bet," as he nibbled into a mark above Dean's nipple.
"What about you?" Dean asked.
"What about me?"
"Do you have any birthmarks?"
"I am a celestial being. Or rather, was. So, no, I do not."
Dean tilted his head. He grabbed the Sharpie off of the drawer next to them, and in one swift motion, rolled them over so he was on top. He towered above Cas, his skeleton breathing heavily above the angel he called his own. "Let's see what we can do about that."
He marked Cas with x's to show the spots he loved the most, laid down dots like sprinkles across the areas he thought were truly beautiful (where his collarbone decided to lift up and kiss his neck; where the faint outlines of muscle on his stomach were), and using his mouth, bit hickeys into him like ink, permanent tattoos to remind everyone that he was his, and his alone.
It was after Dean slept, while Castiel felt the weight of the newly created birth marks and freckles on him that he knew that these weren't where he had died before, but how many times he would die for Dean, over and over.