Runt returned the sly grin I was giving him. Although on his handsome face, it became almost wolfish. My big dick throbbed at the sight of it.
Runt approached me, his tail twitching back and forth with excitement, his thirteen-inch dick hard and leaking pre. "I have a very fun way to make the next improvement..." he murmured, his voice a low, sexy purr. I leaned back against the table, grinning, as the imp came for me. He pushed me back, hoisting me up onto the table, and bent down, leaning in. His long, forked tongue snaked out, and slapped my ass cheeks, giving me a jolt of surprise, setting my cock throbbing. "Oh fuckk..." I groaned, feeling Runt work his way around my ass cheeks, and then tickle my hole. I have never felt anything like it, and my oversized balls shuddered in appreciation. Then Runt was rising, licking my balls, licking my hard fifteen-inch tool, as his hands groped my ass, pulling my cheeks apart, his own hard member pressing against them, rubbing pre on my hole. I groaned softly, and gripped Runt's small shoulders, feeling the firm muscle of his delts, holding on as he got to work, slowly pushing his tool up my virgin ass. I took deep breaths, as unbelievable pleasure filled me, Runt's not-so-runty cock filling my ass with pure hard power. And with every thrust, I cried out in ecstasy, pleasure racing through me. And with every thrust, I grew.
My muscles pushed outward, getting bigger, harder, more powerful. I could feel them changing, becoming heavier, more massive. I groaned appreciatively, my voice dropping, deepening. "Fuuuuuuck..." I moaned, as Runt laughed.
"You like this? You like having a dick up your ass? You like how it's making you grow?" he teased.
I nodded vigorously. "Oh fuck yes... I can't believe how amazing this feels! How insanely awesome!" I grinned back at him, and flexed my chest, which was now thick with muscle. Runt's eyes flashed and he grinned excitedly, as he reached to caress my pecs, his talented fingers sending shivers through me. I growled appreciatively, and grabbed his tight waist, holding trying to pull him deeper into me. He laughed, and started thrusting in hard, while pulling on my thick nipples, squeezing and twisting them, sparks of pleasurable agony racing through me as he fucked me raw. The faster he fucked me, the quicker I grew. I roared with pleasure, loving the sound of my deep new voice. Runt laughed delightedly, and rammed himself home as far as he could, his big cock exploding inside me, filling my ass with his seed. I howled as my body was wracked with one last amazing jolt of growth, every muscle swelling at once. My cock sent a fountain of cum into the air, matching the load Runt had delivered up my ass, the sticky goo raining down on us both. Runt chuckled, and began to lick it off of my huge body, his tongue sending shivers through me, his cock still planted firmly in my ass, pushing in the last of his seed.
Slowly, Runt pulled out, and I stood from the table, which creaked dangerously beneath me. I looked across the room, at the mirror, and gasped. I was massive. Taller than before, with more muscle than I had imagined anyone could have. A huge brute of muscle, bigger than the biggest bodybuilder, my massive muscles easily matching the oversized cock that Runt had given me earlier. I couldn't help but smile, and raise my enormous arms, flexing to admire the gigantic biceps, letting out a low whistle of appreciation as they rose at my command, huge, round, hard, and powerful.