As soon as Derek had finished his massive transformation John realized that it was getting late and he needed to check on the other two of his man-beasts at the apartment. He knew that he couldn't bring both Derek and Francisco (once he drank the vial of pure animal testosterone enhancing juice) back to the apartment, they just wouldn't all fit! So John decided to go get the other two and bring them back to the woods. After all, it was secluded (no one around for at least 6 or 7 miles) and they obviously couldn't go back to conventional society once they had all changed into powerful beasts.
John decided to leave Derek and Francisco in the woods while he went to get the other two. He explained this to them, Francisco, having not yet undergone the transformation understood this better than Derek.
"Why you go?" Derek grunted.
"To get your brothers," John replied, "so we can all be together."
"But I love John, me no want John go!" Derek gave John a big sloppy kiss when he said this, it melted John's heart and he didn't want to leave them either. But he knew he had too.
Eventually John was able to convince Derek that it would be okay. To help distract Derek he pushed Francisco into Dereks massive fur covered arms. Francisco went straight for Dereks giant cock, which was almost as big as Francisco himself. Francisco humped it and licked it, rubbing his big manly muscles all over the gigantic pulsating cock.
John knew he had a chance to slip away.
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Once John had left, Francisco continued to rub himself all over Dereks penis. It wasn't too long before Derek shot his next load all over Francisco, drenching him from head to toe. Derek then grabbed Francisco in his big paws and licked him clean with his big tongue.
All this had gotten Francisco so turned on he didn't know what to do. Then he remembered he still had the vial that John had given him. He popped the cork and drank it in one sip.
Almost immediately he could feel the power welling up within him. He started to let off this deep guttural noise that seemed to resonate within his chest. He looked down at his arms and put a cocky grin on his macho bearded face.
Then he grew!
Taller and taller, out growing Derek by three feet!
Francisco's arms started to explode with muscle and power. His forearms were thicker than most bodybuilders thighs and kept growing larger and larger with dark hair spreading out over them and veins bulging through the skin. His hands started to swell to massive proportions too, with thick knuckles and wide fingers.
Then his biceps and tris started to grow. His biceps swelled to the size of giant bowling balls, rock hard and covered in veins. Then his triceps filled out creating two enormous hams hanging from his arms. His shoulders widened so they were at least six feet across. His pecs swelled and swelled till it seemed they would burst. The man power in those two mounds of muscle on his chest were so big that he could stick both of his big hands into the cleavage and they still be completely hidden. The fur on his chest got thicker, too, and spread down along his hard abs that started to widen giving him a really thick look but still showing off his 8-pack, and down to his crotch. His man bush got even thicker and sweat poured all over his skin.
In between his two gargantuan thighs his cock came alive. All ready hard, it got harder and bigger and wider. It grew and grew till it was 3 and a half feet long and as wide as a 20 liter of soda. His balls were so full of testosterone and sperm that they started to expand as well. Thew swelled and became the size of watermelons, hanging between his hairy powerful thighs.
Then, his neck and traps started to grow first his neck grew to be 45 inches around and then his traps took over. They got so pumped that they reached up to the top of his head and down his wide mighty back. His chin jutted out and his forehead sloped back while his brow thickened. He looked like a cross between a caveman, with his thick black beard and long messy hair, and an ogre with his exaggerated features and teeth that were starting to come up out of his lower lip.
He was fierceom and manly and overflowing with raw power. He grabbed Derek, bent him over and fucked the shit out of him. Both of them roaring like the primal beasts they were.