“Okay,” Cherry said, “I’ll give a game of ‘mercy’ a try. How do you want to do it?”

“I don’t want to do the regular version of bending each other’s wrists backwards.” Heather replied, “That’s a guaranteed way for one of us to end up injured.”

“I see you’ve given this a bit of thought.” Cherry replied, “What do you have in mind?”

“Let’s put your powers to a test against me.” Heather said. “We’ll grab my left hand against your right one, palms together. Since we’re both right-handed, this should give you a good advantage.”

As they got into position, Cherry said, “Now what do we do?”

“It’ll be really simple. I’ll stop concentrating on keeping my biceps down to a tiny size, so that it can go to it’s relaxed size.” Heather said. “That should have my peak touching against yours. Once we’re in place, you flex out to try and force me to give up.”

“What are you going to be doing?” Cherry asked.

“We know that I’m stronger than you, so it wouldn’t be fair for me to try to resist. I’m going to concentrate on staying relaxed.” Heather replied. “I want for you to try and use your hyperflexing ability against me.”

“Are you sure about doing this? I don’t have fine control over that.” Cherry answered.

“You know that you’ve been wondering who’s biceps are stronger, my resting ones or your fully hyperflexed ones.” Heather said. “I really don’t know which you really want to be true, for yours to win or mine, since you kind of like being dominated.”

Cherry’s cheeks flushed pink, “I really don’t know. I mean I like being the high-power superheroine, but I also like the idea that there’s someone who can handle things if I can’t. It’s also kind of fun struggling against your strength.”

“Think of it this way. When you win, it’ll be an incentive for me to try and improve.” Heather answered.

Heather saw Cherry’s bicep fill out, with its peak rising to the level of her wrist. “Getting ready, I see.” She chuckled. She thought, ‘It’ll be more fun if I let my one fill out to its relaxed size slowly. That’ll give Cherry time to concentrate and use her powers.’

As Heather’s peak swelled forward, it met with Cherry’s fully flexed one. Cherry felt Heather’s pulse vibrating her body as the vein at the peak of her bicep pushed into her one. Her own heart was forced into the same rhythm to keep from bursting. Her whole body throbbed from the force of the girl’s heart.

Cherry grunted with effort as Heather’s growing bicep pushed the vein into her arm. She heard her nanites shouting “Structural failure imminent! Systems overload!” She relaxed her own arm down as Heather’s bicep continued to grow towards her. Cherry shouted, “Stop! I give up!”

Heather replied, “You can’t be giving up already. I haven’t relaxed mine out to its resting size yet.”

“Your bicep’s vein is going to crush my arm.” Cherry said. “Your adrenaline is also making your heartbeat stronger. Your pulse is going to burst me.”

“Aren’t you even going to use your hyperflexing against me?” Heather asked, “You promised to try.” She pouted and let her bicep’s peak fill out further.

Cherry winced and yelped. Please stop. I give up.”

As Heather let go, she asked, “You wanted that to happen, didn’t you?”

Cherry held her lower lip in her teeth and nodded slightly.

(Art by https://www.deviantart.com/faogwolf)