Derek was less quick to realize that Isaac wasn't healing, that the claw marks on his thighs weren't scabbing over immediately, that as he gripped his slave's hips as he bounced on his lap, he was leaving bruises behind. He was too lost in the sensations, primal, almost overwhelming in their urgency. He mouthed against the boy's exposed throat, leaving marks with his teeth.
It seemed like Isaac's hole was getting smaller, tighter, but Derek knew it was the opposite--that it was being stretched as it tried to accommodate his knot. A high-pitched whimper escaped him when they were finally tied, finally seated fully, and then he was coming, feeling his orgasm wash over him, oddly slow, as he went still.