Rainbow Dash stared up at Spicy Hot for a moment before she realized the command was for her. Arching her spine and stretching her legs one at a time, Rainbow put on a show for the two lesbians in the room, Spicy, and Twilight too. It felt good to show them herself—all of herself—especially since they couldn't touch.
Turning and looking up between Spicy's legs, Rainbow shifted her weight back on her legs and raised her arms onto his thighs. "I'll try my best, Master, but no promises where you're involved." The excitement in her seemed matched by Spicy's when the moment she unfastened his pants, his hardening shaft tented his underwear.
Spicy had meant it to be a more submissive act than what he was getting. Looking at Rainbow Dash, watching—and feeling—her drag her muzzle around his underwear did wonders for his arousal. Gayness aside, he really liked Rainbow.
Nuzzling and licking at his boxers, Rainbow would normally have ignored her friends in the room, but not anymore. She swayed her rump, almost able to feel Sonata and Rarity's eyes on it. With a few happy swishes of her tail, Rainbow pressed her snout up and nipped down on the top of his boxers, then pulled down.
Marble Pie stared as her friends (she'd come to the conclusion that Rainbow Dash and Spicy Hot were her friends) acted out porn. She watched Rainbow nuzzle under Spicy's penis, licking it from base to tip, then she parted her lips more and lowered her head on it.
What affected Marble more than the sexual aspect involved was the expressions—Rainbow looked to be enjoying having Spicy's shaft inside her mouth more than Spicy did. Having read enough naughty stories to know what should happen next, Marble was nonetheless surprised when Rainbow Dash didn't start bobbing her head. "Aren't you going to—?" She gasped when she realized she'd spoken, cutting herself off.
"I can get off whenever I want. Rainbow will let me use her all day if I offered. This isn't about that, is it pet?" Spicy looked down to see Rainbow shake her head (as much as she could, given her mouth impaled on his penis). "This is a game, Marble. I am making sure Rainbow knows she's my slave. She wants what I tell her she wants."
"You don't want to—uh, um—climax?" Marble was blushing up a storm by the time she was done trying to put words together and getting them out.
Rarity, who had managed to look away from Rainbow's backside only to catch Sonata still looking, kept running her fingers through Sonata's hair. "That's just not always the aim, darling. Even infected with one of those things in my head, I can keep from masturbating to orgasm. Sometimes it's nice just to relax and keep aroused for a few hours."
Climbing up on the couch while making sure her head was never out of Rarity's reach, Sonata curled herself around and lay her head in her lover's lap. "Sometimes you don't want to even be aroused. You just want to be with someone or something that makes you happy." She didn't even notice the gemstone around her neck throb once.
"I should be going." Twilight slipped off the couch and onto her hooves. Part of her wanted to stay, but it was obvious to Twilight that Marble wasn't interested in trying anything further, and with Spicy/Rainbow and Rarity/Sonata paired up, she wasn't going to be getting any further down the rabbit hole tonight. "It's dark enough outside now, no one should be able to see me if I move fast."
Seeing a chance to alleviate her own awkwardness, Marble jumped to her feet. "I-I'll walk with you and make sure you get home okay."
Jerking her head up and off Spicy Hot, Rainbow Dash glared up at him for a second before looking at her friends. "Are you guys sure? I could give you a lift if you want?" As she mentioned lift, Rainbow fluffed her wings.
Memories of her previous time riding on Rainbow's back dominated Twilight's mind. "No! I mean, no thanks. We'll be fine."
The walk to Twilight's parents' home—and now she was acutely aware that it was their home—went by both without word or incident. Instead of going through the house, Twilight walked around the side of the house and to the basement doors.
"Would you like to come inside?" Twilight asked Marble.
Worry struck, and Marble realized she'd maybe-kinda-sorta escorted a friend home to what might have been assumed to be a sexual encounter. "I-I-I should g-go."
"Can I just run a test on you? I want to know the status of everyone's parasite. Rainbow's looked really advanced compared to the others." Twilight used her magic to open the door and start heading down.
"Just one." Marble walked down the stairs carefully, following Twilight and even closed the doors behind her. Then she looked around the basement. "Whoa. Where'd you get all this equipment?"
Twilight Sparkle felt a minor blush fill her cheeks with warmth. "This stuff? I made a lot of it myself, it—"
"Twilight!" Spike rushed across the room and grabbed up Twilight to hug her. Being three times her size made this a particularly easy thing to do. "I thought you were going to be gone forever!"
Hugging back with her forelegs, Twilight shoved her snout into the soft fur of Spike's chest. "Spike! It's so good to see you! Oh! Spike, this is Marble. Marble, this is Spike. He used to be my dog, then he started talking, and then we had an accident with magic and…" She trailed off because Marble was completely distracted from the big anthropomorphic canine in the room. "Marble?"
"Oh man." Spike put Twilight down and face-palmed. "Another geek?"
Marble's attention didn't waver from the spectrum analyzer until she felt Twilight brush up against her leg. Her eyes narrowed down to points, and she backed away. "S-Sorry. I didn't meant to—"
"It's pretty cool, isn't it?" Twilight asked, having to rear up on her back hooves to be able to reach the counter top the device was sitting on. "My dad found it at a junk sale from the university, and when no one knew what it was he got it for me. Anything you want to test?"
Marble Pie woke up somewhere other than her own bed. Her mind kicked into freak-out mode and started trying to makes sense of things. She'd been with Rainbow Dash and Spicy Hot at Spicy's house, she'd helped hypnotize Rainbow, then she'd felt awkward and taken the first exit she could.
Twilight Sparkle was laying against Marble's back. She could feel the warm crystal of Twilight's body pressed against her clothed skin. Clothed. Marble's panic lowered a few notches—she was still clothed.
As Marble came to terms that she was sleeping in a bed with Twilight Sparkle, she started remembering what had happened. Science. They'd run scans on each other, Marble had suggested some extra tests that Twilight hadn't thought of, and Twilight some that were new to Marble. By the time they were done with each other, they had even more questions about their physiology.
But there was something important that Marble couldn't say no to. Her belly twisted in a knot as need built, and her mind turned to the "emergency dildo" in her bag. She lifted her head and scanned the room, trying to remember where her plaything would be.
Reaching out from under the blanket, Marble Pie grabbed at the bag she spotted—that was right beside the bed. Her hands moved quickly, unzipping the bag and delving inside to find her relief.
Like always, the more aroused she got the less sense her mind made. Marble turned the vibrator on and brought the buzzing unit under the covers with her and quickly to her entrance. She was wet already, that was never a problem, and as Marble started sliding the vibrator into her needy depths, the buzzing became muted.
Waking at the movement against her back, Twilight froze at the sound of buzzing. "W-What's going on?" But, when Marble moaned into a mouthful of blanket, Twilight realized what was happening. "Wait, the parasite is doing its thing, right?"
Lost in her chemical-induced fantasy, Marble barely heard Twilight's first question, but she whined and nodded to the second.
"This is great! We need to see why it's doing this. Can you come over to the scanner?" Jumping from the improvised bed, Twilight walked over to the scanner, but when Marble didn't follow, she looked back at the girl. "Are you coming?"
"J-J-Just about," Marble said.
"Wait!" Twilight used her magic to reach out to Marble's wrist and pull it back from her body, but when Marble cried out as if in pain, Twilight let go of her wrist and picked Marble up completely. "S-Sorry. But we need to scan you."
Screwing her eyes closed, Marble Pie didn't want to think about what was happening. She'd slipped out of her pants under the covers of the bed, which meant she was half naked and couldn't stop masturbating. Ignoring what Twilight was doing, she worked with the toy and pushed her pleasure higher and higher until finally her reward came.
Twilight stared in surprise at the rush of activity within Marble's head. She could actually see the slow growth of the parasite, and watched as new connections were made in Marble's head. "This is amazing! Marble, you should see—Oh, right. Uh, you just finish up."
Marble sincerely hoped Twilight would just stop speaking. As it was, she couldn't block out the fact that someone else was watching her masturbate. Rainbow had been one thing—they were both dealing with it together—but she barely knew Twilight Sparkle.
Then it hit her. Marble Pie curled her legs under the chair tightly and clenched her teeth as her body shook in release. The rewards her brain was fed for complying with the parasite were many, but not the least of which was a boost of brain-chemicals to reward behavior.
Opening her mouth at last, Marble let out a sigh and slumped in place. She didn't want to lift her head and look at Twilight, but there wasn't anything else to do. When she saw Twilight standing on the same seat from the previous night—looking into a display that looked like an x-ray of Marble's head—Marble couldn't stop a little smile from chasing her frown away.
Twilight Sparkle, Marble had come to find out, was a scientist. Not just a regular one, a mad scientist. When there was something that needed observing, Twilight would do just about anything to observe it—which included Marble's head. "W-What happened?"
Not looking away from her display lest she miss something (and totally not because Twilight got a little embarrassed at seeing marble naked), Twilight gestured to another seat beside her. "I've observed a two percent growth in the parasite's mass over the course of your——This is amazing, Marble. Come and take a look."
Looking back to the bed, Marble scurried over to it and quickly stuffed her toy into a sock. She pulled on her underwear and pants, and ignoring the damp feeling in her panties trudged over to Twilight and froze as her eyes fixed on the played back image on screen. "Th-That's growing a lot. It did all that while I was—um—err…"
"It did!" Twilight finally peeled her eyes away from the screen to look at Marble. "Almost makes me wonder how long it would take to grow to full size if you—"
"If I—" Marble had no better luck finishing the statement than Twilight did. "I'd be raw by the end of it."
"Not if we took precautions." Twilight's brain didn't slow down as it raced to plan out a day of forcing Marble to climax constantly. "Besides, it's not like you need the physical stimulation to keep climaxing."
"I don't?" Marble Pie was blushing up a storm, despite her curiosity in what Twilight was thinking about. "W-W-What would be needed?"
"Well,"—Twilight reached up to her brow to push glasses that weren't there with a hoof that wasn't a hand, it almost distracted her—"with the right electrical stimulation, you'd just need to start going and we could play back the pleasure sensations and keep you at whatever arousal is needed."
"I-Is this an experiment?" The idea of being hooked up to a machine—of not being touched or even physically stimulated—interested Marble enough to almost make her squirm. "I mean, c-can you build something to do that?"
"When would you next have to feed your parasite?"
"Midday."
Twilight gave Marble an awkward smile, trying to push science and "I couldn't do it alone, but if someone helped me…"
The consummate nerd and scientist in Marble almost jumped at the chance, only to be backed up by the naughty side of her brain. She was intrigued, horny, and felt like building something. "O-Okay. First we need the interface with my nerves. Do you have any way to do that without—well—surgery?"
Over the course of the morning, Twilight had been surprised many times by how capable Marble was, and how quickly she could pick up on Twilight's ideas. The more useful thing to Twilight was how quickly Marble had gotten used to working with a magic user. Since the loss of her hands, Twilight had quickly expanded her magic telekinesis to pretty much everything she did.
The interface box they'd assembled, with the special collar installed around Marble's neck, could differentiate different nerve impulses and play them back. They'd started with the feeling of her finger tapping against the desk, and had progressed to Marble poking and prodding various bits of herself and giggling when she played them back.
What Twilight had noticed, as the morning worked toward midday, a level of background noise was increasing. It was a mix of all kinds of senses, none of which Twilight was willing to mess with. Touch was all she allowed herself—she didn't want another turn-someone-into-a-pony incident. "Are you ready?"
Marble's head shot up from feeling the repeating sequence of taps on the back of her right hand. "What?"
"Are you ready to try it? We've done tests, and I think I have the calibration worked out. Are you ready to see if you can—uh—train it, then have it do a playback?" Despite knowing full well what the aim of their work was, Twilight still had trouble saying it, mostly because Marble seemed to have the same problem.
Being forced to masturbate—not having any control—was a far different prospect than what Twilight was suggesting. Marble wanted to say no, to take off the device and run away to her safety back home, but she'd actually bonded to her second person outside of her family. Twilight seemed to have the same kinds of ideas she did, and for once she felt like someone just got her own.
"C-Can I get something to eat, first? And is the door locked?" Marble asked.
As realization sank in that they'd gone all morning without food or drink, Twilight's belly let out a plaintive rumble. "I think that's unanimous?"