"I think you will show us by example what the goo is capable of," Erika said in a decisive tone. "Emily here is getting a little excited, so you will make her cum. With your mouth. In front of your girlfriend."
Sam blushed for the first time while most of the other girls giggled. Cole tried to resist the order but felt compelled to turn to Emily, approaching her on all four as his own body seemed to betray him, his red rocket hardening to full mast. He couldn't take his eyes off Emily's smaller member as she sat on her knees.
"Go on then, show us how it's done if you think you're the expert," Erika grinned, crossing her arms over her toned chest.
Cole's face lowered closer to Emily's twitching member, and he caught a whiff of her pheromones. Instantly, something clicked in him, and Emily's semi-erect cock was all he could think about. His head reached even lower as he took it inside his mouth and began to suck, the shape of it transforming from human to more canine as he felt it swell over his tongue.
"See, the goo that shouts from our 'male' parts has a special effect, which you will discover in a moment," Erika continued.
Meanwhile, Piper, Riley and even Sam were sitting on the couch, hypnotized by the scene. Everybody could see Cole's own cock getting erect as he sucked on Emily's, and some beads of fluids were even dripping from its tip. He bobbed his head up and down a little faster, making Emily squirm and pant. Her knot expanded in front of his eyes and the beads of fluids turned to a continuous oozing as Cole became more excited himself.
Piper pointed to his throbbing canine member: "Look at him Riley! I think he enjoys this more than he wants to admit."
Riley laughed and turned to Sam: "He's so red and big, haha! And so obedient. Aren't you proud of him?"
Sam blushed harder, a little turned on at the sight of her breeding mate in this position. She didn't think at all about how strange the situation was, all of them naked in the room. In fact, it was oddly comforting to share this secret together. She watched intently as Cole increased the pace and Emily let out a few moans.
"Make her come, Cole," Erika ordered as she had crept closer and put a hand on the back of his neck. She pushed down on his head until his lips wrapped around Emily's knot, whose hips started bucking wildly.
Cole executed himself, trying to ignore how incredibly turned on the situation had made him. There he was, entierely naked, his canine rod leaking pre all over himself and the floor, sucking on a girl's mutant cock while a bunch of hot girls were watching... Fuck he was a real pervert, and too weak to resist.
Suddendly Emily howled lewdly as she cummed in Cole's mouth, who didn't gag and hungrily gulped down as much of the stuff as he could. Emily's dick kept overflowing though, and goo started running down Cole's mouth and chin, dripping on the floor noisily. Emily dislodged herself from Cole and fell on her side for a second, and Cole felt the urge to lean down and started licking the cum right off the floor.
"Haha, look at him go, he's so dedicated," Riley joked.
Cole then sat looking up at Erika, a little out of breath, when the changes hit his body. All the girls in the room watched at his leaking dick became shorter and shorter, and his ballsack shrank as it pulled into his body. At the same time, his natural moobs expanded forward, becoming rounder and very feminine, until the swelling orbs looked very much like Riley's and Piper's breasts. Smaller changes also affected his waistline and frame; a narrower waist, plump butt, smaller shoulders. He was a girl now.
"What a good girl you are! And definitively the omega here..." Erika grinned again, patting Cole on the head. "And this is the effect of the goo, although it is not permanent. After a few hours, he should revert back to his usual self. But meanwhile he'll be like this, and also very horny."
Cole was slowly coming back to his senses. Looking up at his girlfriend Sam, he felt a little guilty - but not as ashamed as he wished he was. Mostly he was embarassed about how good what had happened felt to him, a hard truth to face. Sam's expression though was difficult to decipher, and he wondered nervously what she was thinking of him now.
At this point Erika was getting a little pent up, sporting a full mast of her own. Everybody's eyes turned back to her, eagerly awaiting her next decision.