Lewis came to the best orgasm he ever had in Dei's mouth, his cock softening. Dei slowly pulled his mouth off of Lewis's cock, squeezing his lips as he did so. The tingling persisted, and Lewis stared as his cock and balls slowly grew. First to large but relatively normal human proportions, then further to the bounds of human possibility. They kept growing, and a dawning sense of horror reached Lewis as his soft, fattening, cock reached his knees, his balls swelling proportionally to match. Further, still, it grew, only stopping when Lewis felt the grass of the clearing tickling at his urethra. Dei stood up, and forced an open-mouthed kiss on the horrified young man. Lewis felt his voice returning to him.
"...What did you do to me?" He was clearly fighting back tears.
"A bigger cock, just as you said you wanted." If Dei knew Lewis was upset and horrified at what had transpired, his demeanour didn't show it. "Now, it's time for you to go back to the forest you came from," Dei said with an almost wistful lilt, turning away from Lewis, walking towards where Lewis's clothes were piled. Bending to pick them up, he turned back towards Lewis "I'll be keeping these as payment for services rendered. Have fun with your new toy."
Dei's voice faded, as did the clearing. Lewis found himself facing a tree, his now monstrous member touching it. Looking around, he couldn't see the trail, and he wasn't entirely sure what the way towards it - or more directly towards his home - was. Or how he would manage to walk with this... Thing... between his legs.