His hips were–
I looked down.
Oh.
His cock was proportional to the rest of him. Thick and heavy, already hard, jutting from the sheath at his groin. It wasn't shaped quite like a human's, broader at the base, with a slight curve, the head blunter. And there was something else, a swelling near the root that I didn't have the brain cells to think about right then.
"It will fit," he said, reading my face. "The serum adapted your body. You were made for this."
"I wasn't made for anything–"
He shifted his weight, and the head of his cock pressed against me, and every thought in my head shattered.
He worked me open without rushing.
I don't know how long it took. Time had gone strange, breaking into moments of sensation with nothing connecting them. His fingers first, one, then two, then more, stretching me in ways I'd never been stretched, my body yielding to him with an ease that should have frightened me. His mouth on my breasts the whole time, sucking, licking, that rough tongue working my nipples until they were swollen and tender and so sensitive that every touch sent sparks down my spine.
When he finally pressed inside me, the real thing, not his fingers, I sobbed.
He stilled at once. "Pain?"
"No." The word came out broken. "No, not – just – more. I need more."
His tail lashed. His hips pressed forward, feeding me another inch of that impossible cock, and I felt myself stretch around him, my body opening in ways it never had before. The serum, I thought distantly. The serum did this. Made me able to take him, made my body into something built for this exact purpose.
I should have been horrified.
I wasn't.
I was full. Fuller than I'd ever been. He was so deep I could feel him against my cervix, that broad head pressing into places no one had ever touched. And he was still going, still feeding me more of himself, that swelling at the base getting closer with every slow thrust.
"The knot," he said, his voice ragged. "When I – it will swell. It will lock us together. The first time is–" He broke off, shuddering, and I felt his cock pulse inside me. "It is intense."
"Do it."
He looked down at me, those huge dark eyes, the heavy curve of his horns above his face. He breathed me in.
"Mara–"
"Do it."
He thrust forward, and the knot breached me, and the world went white.
I came.
Not once. Not twice. I lost count somewhere around five, my body clenching around him in waves that seemed to go on forever. The knot swelled inside me, holding us together, stretching me to the edge of pain and then past it into a fullness that was too much and perfect at once. Every time I thought it was over, every time I was sure I couldn't possibly come again, his hips would shift or his cock would pulse and I'd tip over the edge once more.
Somewhere in the middle of it, his mouth found my breast.
He'd been paying attention to them all along, touching and stroking, his rough fingers working them while he fucked me. But now he latched on, sucking hard, and I felt something give.
Warmth. Wet warmth, thin and sweet, flowing from me into his mouth.
He went still.
Completely, absolutely still. His whole body rigid, his mouth sealed around my nipple, his cock buried deep inside me. His tail stopped moving. I wasn't sure he was breathing.
Then he swallowed.