For Purely Scientific Reasons

Shining Armor headed across the street and noticed the oddest of sights exiting from Twilight’s castle. With a large grin plastered on his face, the immense red stallion shut the door to the house before running a hoof through his mane. His face was flustered something fierce.

“Hey, Big Mac!” Shining greeted, waving a hoof.

Any trace of a smile on Mac’s face shrunk to a thin line as he viewed the unicorn. A deeper shade of red bloomed in his cheeks while his eyes popped out comically.

Shining ignored this. “Did Twilight want to speak with you too? About the research she’s conducting?”

Big Mac scanned both ends of the streets anxiously. “Nope,” he muttered.

Shining furrowed his brow. “But I just saw you leave Twilight’s house.”

“Nope,” the stallion repeated, nodding in commitment.

Shining waited a moment, viewing Big Mac and then the towering castle only a few paces behind him. “You know the door to her house is in leg’s reach, right? Like directly behind you?”

“Nope. Gotta go.”

Without another word Shining was left in a small dust storm as Big Mac galloped away, unmindful of the few wandering ponies he nearly knocked down. At the end of the block he readjusted his direction, almost collapsing a fruit stand. Shining had never seen the big guy move with such speed—or speak as adamant as then.

He thought, Whatever Twilight must be researching must be something top secret.

With a hoof against the knob, Shining entered Twilight’s castle.

***

“Twilight?” he called from the entryway. “What in Equestria did you do to Big Mac?”

Shining heard the sounds of running water as he entered the cozy living room opposite the kitchen. On the table were a series of tall, clear jars with labels on each. On each label were written two initials, the last one reading “B.M.” That one was close to three-quarters full with a white, translucent liquid. The jar right next to it was empty with a label waiting to be filled.

“Just a second, Shining!”

The stallion turned away from the table of jars and toward the small bathroom near the kitchen. The door was propped open ajar and he could hear his sister frantically brushing her teeth and gargling out water. It was cute how she still refused to let her mane down around him—even if she only wanted some help with her latest study task.

He regarded the thick liquid in the dozens of jars. “Are we doing some sort of paper mache project, Twilight?”

“I’ll explain in a minute!” she called, before he heard her briskly wipe her face with a towel.

A moment later she exited the bathroom and fixed him a warm smile, a small twinkle shimmering in both eyes. “I’m glad you made it, big brother. A little early though, I only just got through with Big Mac when you came.”

“I like to be punctual. You should know that. Seeing a lot of research ponies today?”

“As many as I can fit in. Make yourself comfortable on the couch.”

Shining edged toward the puffy couch and settled in the middle. He placed one hoof on the other, waiting for the demonstration or explanation that was surely to follow. Instead, Twilight levitated a white- and purple-striped sock to him.

He held it up for inspection. “A sock?”

“A test,” Twilight corrected, sitting awkwardly on the edge of a chair. “Slip it over your horn. I want to see if something I’ve been working on actually works.”

“All right.” Methodically Shining slipped the (hopefully washed sock) over his horn, making mental note that it nearly fit like a glove. When he had it down to his mane he waited a moment for something to happen. “So what should this do?”

She answered, “Try and move something with your horn.”

The white stallion searched the room before deciding on a book on a counter. He mentally flicked at it and discovered nothing at all was happening. “That’s amazing, Twilight! A device that stops the use of magic altogether! What do you call it?”

“Magic sock,” Twilight said bluntly, edging her purple rump from the chair and gingerly stepping towards him. “All right, before we start, I need you to relax and place both forelegs above your head.”

“Uhh…” Shining hesitated before lifting his legs behind him so they rested near the top of the couch. “Okay.”

Twilight was right in front of him now. “Now spread your legs a bit and come forward on the sofa.”

Although Shining trusted his sister wholly in the department of safety in the quest for all things knowledgeable, a small flicker of apprehension tickled his chest. Still he slid his butt down the seat, keeping his forelegs where they were. “Is this all—”

Swiftly, Twilight grasped both his thighs and shoved them apart, a stern expression of deft concentration on her face. She nodded. “There. That should work. Now all you need to do is keep still and we should have you out of here in no time.”

Shining’s apprehension only grew. “Why do I feel nervous all a sudden?”

“Because you’re not relaxing. I told you to relax.” She backed away a bit, admiring him in his oddly struck pose. “Comfy?”

The stallion thought blatantly, At least she said it’d be short. “Sure,” he answered.

“Good.”

Twilight lowered her head and directed her horn at him. She charged up a small purple and white ball that grew into a thin wave. One flick of the noggin sent it outward, where it hit every item in the living room, including Shining. Despite his best efforts, he grimaced from the sight.

Eventually he opened his eyes. “That wasn’t so bad.” He waited another moment—for some hidden after effects to come wallop every one of his senses. When he found none to discover he tried to sit up, only for all four of his legs to be held rigid in place. His head could turn from side to side and his torso could shove around the smallest of degrees, but he was fixed tight to that couch… and in the weirdest of stances.

“Why can’t I move?” he asked her, already fearful of the tiny smirk on her lips. “I think this spell’s been discovered already, Twilight. You might have to try something different.”

The alicorn shook her head. “No, it worked fine. This is only the first part. I told you I couldn’t have you moving around during our research.” Slowly she trotted between his drawn out legs, placing both hooves on his thighs. “Still comfy, big brother?”

Shining’s eyes bulged while his jaw tightened. “What are you—”

With relative ease, Twilight lifted herself towards his face, her breath warm on his splayed body. She stopped near his ear. “Tell me when you’re uncomfortable.” Then she carefully kissed one of his reddening cheeks.

“Now,” he said bluntly.

Delicately she plucked him a few more kisses, holding one side of his face with a free hoof. Her last one landed on his lips—lips that had tried their best to retreat back into his mouth.

“Now!” he exclaimed. She then pulled away to smooch longingly on his heated neck.

“Just making sure, Shining,” she told him. “I don’t want to start something unless we’re on the same page.”

She scooted off the couch and viewed him with a studious expression. Shining breathed out a sigh of relief that quickly turned into a yelp as his sister placed a warm hoof against his sheath. Once there, she rubbed it in slow circular motions.

Twilight looked as though she barely knew she was doing such a terrible thing. “The row of jars behind me contains several different samples of stallion semen. I’ve kept the process of collection with each as close to the same as I could—the difference between them is their relationship to me. I’ve collected from complete strangers; from friend’s relatives; from close friends here in Ponyville; but the only sample remaining is from one of my own siblings. Which is why I asked you to come today.” She paused. “I mean come here today.”

During her speech the gentle motions around his groan sent small shivers of pleasure to the stallion. His mind was a flurry of horrific thoughts, the largest being that his very own sister was touching something she shouldn’t have even been near. But another—far more pressing concern—was that things were starting to move and harden underneath her carefully moving hoof.

Shining had to think fast before he’d never be able to look at his sister the same.

Unless… he thought.

“Queen Chrysalis, I presume!” he shouted to her in his most heroic of tones.

Although the Twilight-impersonator did not blanch from his clever deduction, he could see her face contort in confusion. Her busily moving hoof had now found a few inches of workable length to slowly stroke from the base. Shining forced himself to ignore the newfound wave of small pleasure.

He continued regardless of his hanging ponyhood. “You thought you could mask yourself as my sister and sour her good name! Any moment now and I’m sure she’ll return to triumph over you! Your original plan at my wedding might have won me over for a time, but your latest plan won’t even get off the ground. Surrender now and I will see you live to plot another day!”

The Twilight-impersonator slid her other hoof under his balls to rhythmically tease them up and down. The other hoof had worked his member close to full attention, before carefully sliding along every last inch that had previously flopped onto his stomach. Every few strokes, she’d stop near the tip to crease every soft nerve. Already a small bead of white was resting on his head.

Ignoring her—ridiculously—pleasurable work, the Twilight-impersonator lowered both brows and glimpsed the near panting stallion above. “Why would Queen Chrysalis ever bother with stallion semen extraction? She wants love… not that kind of love, Shining.” She shook her head. “Sometimes I wonder how we’re related…”

Shining’s entire length was close to throbbing. The hoofs working under his length and cupping his balls pulled at both large objects playfully. The other hoof gripped the top of his shaft to rub right on the tip. The usually white-faced stallion (but now very red and white-faced stallion) gulped dryly.

He viewed his sister with pity in his eyes. “Please say you’re Chrysalis… or a changeling… or something that isn’t my sister!”

She shook her head. “Sorry, Shining. That’s not the case this time. But we’re almost there. So sit back and relax and if you really want, just pretend I’m Cadence or something.”

He mumbled, “Cadence hasn’t done anything like this since the wedding.”

“Then I guess that makes me a great sister.”

Twilight levitated a small band with her purple aura and swiftly slid in down his member to the bottom. Once there she let it go and it tightened around, constricting the blood and making his long member throb with each heartbeat. With that done, Twilight took a second band to tie her hanging mane back. She opened and closed her jaw in large stretching motions.

Gripping his solid length between both hooves, she brought the tip close to her mouth to playfully lick. With the oddest of sensations, Shining watched as his little sister swallowed the small drip of cum from the end of his shaft. Something inside him died at that moment—while something far more perverse awakened from within.

“Tell me when, Shining,” she said, staring intently. “I don’t want to miss a drop—that would only ruin the experiment.” Then she wrapped her limber lips around the first few inches of his penis, tongue first wrapping around everything it could.

Shining’s chest beat away like a heated stove. He flung his moveable head to the back of the couch and tossed it from side to side. It was all too much. Much too much.

“Please tell me you’re not going to swallow!” he blurted, such words tasting like dirt on his tongue. “Please don’t, Twilight! Please!”

She removed her working mouth from his slick member, a wet plop! sound as she did. “Don’t be gross, Shining. I’ve created a spell that once your seed reaches a certain part in my throat, it’ll be directly teleported to the empty jar on the table.” She rolled her eyes. “This isn’t for fun, Shining. It’s for science!”

She lowered her head to his shaft again, forgoing the first few inches to devour all that she could muster. The muzzle on his sister only added to the experience, as she could take close to half of him before his tip would bounce against the back of her throat. With her two empty hooves, she ran them along the remainder of his shaft, working in horrific tandem with her bobbing head and sucking mouth.

She’s had practice, the now sweating stallion thought. She had all morning to practice.

Unwillingly, Shining returned his reddened face to the cool confines of the headrest on the couch to twitch uncontrollably from the actions below. Although he wasn’t watching what was happening, each fast and wet sound met his ears and each brutally wonderful sensation claimed what righteousness he had originally held claim to since he’d entered Twilight’s home.

Until Shining could barely contain his soft moans (ones that sounded sadly close to whimpers), his little sister worked away on his hard member, shoving more and more of his warm and pulsating length into her tightly sealed maw. While one hoof stroked near the base of his penis, another rediscovered his wide pouch sitting idle on the couch, caressing them as softly as a lover’s kiss. And just like that it had become too much.

Oh Celestia, he thought. No, please no!

Finally he pried himself from the couch to watch his busy sister—his member about to erupt from the weeks of inactivity back at the Crystal Empire. He told her bluntly, “You will not get what you want today, Twilight. You can try until you’re blue in the face but I’ll only leave you disappointed. So stop now and we’ll forget all about it.”

He gritted his teeth as she unhooked her mouth from him, her hooves still running up and down his length, keeping him going. Such a lie, he thought. Such a flimsy lie.

Twilight looked unperturbed. “Now you’re being silly, Shining. When it comes to science and everything book-tacular, I always get what I want. Now stop talking; I know you’re close and I’d like to finish before the next appointment arrives.”

“But—” was all Shining could blurt, before the warm and wet lips of his kid sister found the remainder of his shaft. Forgoing her original strategy that had already placed him close to ecstasy, Twilight doubled her efforts, speeding along his penis in hurried and rough intervals. Both hooves returned to the lower half of his shaft, tightly pulling at what was barely held within. He watched as she lit her horn, before feeling his balls coated in a thin aura, squeezing and loosening. Obviously Shining knew what his sister was after.

As much as he wanted to retreat from the sight, he found himself locked on the act. Nor could he shut his eyes to pretend it was only Cadence treating his body in such a miraculous manner—no, it was his younger sister and Shining had never thought something so sickening could tug at his up-until-then innocent arousal in such a way.

But no one will know, he tried to reassure himself, as he first felt the hints of the outward explosion. Unless she publishes the results. Would she? Oh Celestia—

Shining was instantly torn from his thoughts as Twilight unfurled her wings to wrap around the edges of his plot. Matching the speed of her bobbing head, she lifted him from the couch to smash into the back of her throat. Even though Shining from that day forward would never admit to such an act, he sadly thrusted right along with her wings, wanting to push himself all the way inside her warm and wet jaw.

“Oh crap…”

A few seconds after she had added the wings to the procedure, Shining shut his eyes while his hips locked in place. When he began to cum inside her, Twilight grabbed the sides of both legs to hold him in place. As each large and heavy load spewed out, his legs twitched from the overwhelming sensation. Head slamming into the couch, he silently moaned as each hot load was greedily accepted by the still latched on alicorn.

Every shot was followed by a near choking swallow. If Shining hadn’t been busy riding out the largest orgasm of his life, he might have even been proud, as his own batch of semen first flew into the empty jar from a small purple aura at its top—already tying with Big Mac’s amount, before shooting a good centimeter above.

“Ugh.”

When he had been dried clean, Shining collapsed back to the couch and felt each sweaty limb return to his control. Even though he had merely sat and watched as someone else rode him out harder than he could believe, he could scarcely remember a time when he felt more horrifically winded. With heavy eyes he watched Twilight get to her hooves, twisting her neck and wiping at her mouth as she did.

“See, that wasn’t so bad, was it?” she asked, fixing him a grin that didn’t little to salvage the situation. With her horn she removed the magic sock from his head and flung a towel onto his damp chest. “Clean up quick, please. My next subject should be here soon, and I would hate to greet them looking so disheveled.”

She spun, and right before exiting the room set a new jar on the table with the rest, before labeling the freshly filled jar with, “S.A.” in thick black marker.

Nerves still shaking from the experience, Shining hastily ran the towel over his wilting member and other moist regions. Then he got to his hooves and wobbled in place.

From the bathroom he heard Twilight start the sink while she brushed her teeth vigorously. She even hummed as she went.

And now I try and forget this ever happened, he thought, as he stumbled towards the entrance.

A moment before touching the knob, the door swung inward and a familiar sight greeted him.

“Hi, Shining. Did Twilight want to see you today too?”

Shining closed his eyes and brought a hoof to his temple, suddenly curious about the current costs of therapy sessions. He finally said, “Hi, Dad.”