As Jess grew even bigger once Randy came, he knew he had to do something. The sight of Jess’s huge muscles and sexy shape was enough to drive him over the edge. But he also saw what Jess did to Brad and he wanted none of that. So he quickly decided to do what any he-man would do. He played possum. As soon as he finished coming the first time he shuddered, closed his eyes and went limp. He then thought about baseball, his Grandmother and his math homework. Anything to keep himself soft. And fortunately for him, Jess bought it. Growling, she pulled him out and tossed him to the side and he thumped on the ground and rolled over toward the far wall.

“Worthless piece of shit. No wonder Amanda only grew this size.”

At 7 and half feet tall and filled with massive, bulging, intimidating muscles, Jess smiled up at the confused and not as scared as she should be Amanda. Amanda looked down and pleaded. “Please Jess. This isn’t like you. You’re acting like some power hungry nut.”

Jess growled again and tossed Amanda against the other wall and shook the room as Amanda thudded to the ground.

“Shut up you. I should snap your neck for talking to me like that.”

As Amanda pulled herself up slowly, unsure of Jess’s strength level or hers, she figured her only chance was to make a dash for the gun and hope that Jess’s large form would slow her down. But then Amanda’s eyes widened as Jess began to shrink. However, she wasn’t shrinking fast enough and was eyeing Randy again. That was the opening she was looking for and took a dive toward the door. But Jess turned quickly and swatted Amanda back against the wall with another room shaking crash.

“And where to you think you’re going?”

As Amanda wiped the blood from her face, she turned to her side as Jess shook her head as though she were clearing out some cob webs. She had also lost a few more inches. Amanda tried to piece things together. Sex with Randy once caused the spike in strength with no growth. Amanda guessed the same happened with Jess. But multiple orgasms were too much for Jess’s system and her body swelled with muscle, causing her to grow taller too. Maybe it also had something to do with her misdemeanor, which was completely different from the sweet Jess Brad had fallen for. However, Amanda couldn’t be sure of anything. And unfortunately, Jess did remember something.

“Ah Ha! You were going for the gun! Well you can forget it! I’m going to get it! Now you stay here or I’ll rip your head off!”

With that Jess stormed out of the room, lumbering forward as if she were unsure where she was headed. Amanda got up slowly and looked at the two boys. Brad was groaning, but was now sitting up. “What happened?” Randy sat up too.

“Holy shit, Amanda, we need to get out of here.”

Amanda bit her lip. Go where, she thought. No, their only hope was make Amanda stronger than Jess. Amanda rubbed her chin. “Alright you two. This may sound crazy, but ..”

As Brad shuddered, Randy sighed.

And before the boys knew it, the effects of the gun on them became clearer. They could get hard in a hurry and orgasm almost as fast. As Amanda closed her eyes, holding her brother over her head and sucking, Randy was feeling Amanda’s muscles and doing her standing up. And before any of them knew it Amanda was growing, receiving double doses in half the time. Unfortunately for the boys, not only were her muscles expanding at an alarming rate as her height increased, but her demeanor was changing too. Brad came a second time and slumped forward, exhausted. Amanda was now well over 6 foot tall and still growing, her muscles now pressing out in every direction. She pulled Brad high above her head until he was brushing the ceiling.

“You worthless piece of garbage. You only came twice? No wonder Jess had to move on to Randy.”

She tossed Brad down hard on his already broken bed where he bounced off and spun away until he slammed against his closet door. Amanda picked up Randy with her now free hand and pulled him up as her height approached 7 feet tall.

“And as for you, it sure didn’t take long for you to get hard for Jess. Well take a look at my muscles! I’m bigger than Jess was! And you had better show me you care, mister!”

Randy, already hard was also wincing in pain as Amanda was using him as a human dildo, smashing his body into her steel frame. He decided to try the same tact with Amanda he had used with Jess. Once he came again, he went limp.

Meanwhile Jess was walking around rather slowly, bumping into walls and furniture and smashing them against her steel hard body. By the time she made it to the weight room she was under 6 feet tall and her muscles continued to shrink. Looking around she noticed that all of the weight was resting on one bar. Sniffing, Jess walked toward the bar.

“So, I’ll bet Amanda thought she was sooooo strong when she benched this.”

Reaching out with one hand, Jess lifted the bar up over her head with ridiculous ease.

“Ha! It feels like a feather to me! I’m the strong one around here!”

Eyeing the gun, Jess dropped the bar to the ground with a crash and moved toward it. “So this must be the gun that got everything started.”

Now down to just over 5 feet tall, Jess’s body was returning to her original size, but now her muscles looked as though they were carved from marble. See peered at the gun settings to see the muscle was up all the way and the height down to zero. “Hmm. Well I guess I’ll take this back up to Brad’s room, and…”

As the last of the pumped up growth diminished and Jess was back to original height and muscle size, she shook her head as her attitude switched back to normal. “Brad! Oh my god, what did I do? I’ll never forgive myself if I hurt you.”

Turning toward the mirror she gasped. “And I’m butt naked too. What is going on?”

With the gun in her hand, Jess raced out of the weight room and back up the stairs, walking in just as Amanda was tossing a limp Randy to the side.

“Another piece of garbage! If you two weren’t such great power batteries I’d take you both out!”

Jess stood in the doorway in total awe. Amanda was nearly 8 feet tall and her muscles were nothing short of boulders exploding off ever part of her body. Large veins were pumping viciously across her ripped frame. She was nothing short of a muscle goddess. Amanda turned toward the door to see Jess staring at her.

“And as for YOU! Where is my fucking gun!”

Jess pulled the gun behind her back, looked up at the hulking Amanda and gave her a weak smile. “Uh, what gun?”