Rainbow Dash walks through the alley behind Ponyville's joke shop on her way back from a hard day (or at least a hard few minutes) of work regulating the town's weather. She's entirely minding her own business – to be specific, she's fantasizing about being in the Wonderbolts full-time, and no longer needing to worry about whether or not there are clouds in the sky in any particular place.
Noises come from behind her: hoofsteps, an empty can rattling.
Rainbow whirls around, instantly ready to face whatever villain might be following her. To her shock, though, it's Mare Do Well's blank purple face staring back at her. The only pony who ever bested her (even if it had to actually taken five ponies in order to do so). Mare Do Well stalks toward her in total silence, no word, no gesture to indicate her intentions – she doesn't even blink.
But Rainbow already knows this masked mare's secret. (Honestly, she thought she'd never have to see this silly costume again, once she pulled off that mask.) She isn't concerned; she grins and raises a hoof in greeting. “Hey, how's it going, um... Pinkie?”
No answer.
“Twilight?”
Still no answer.
“A-J?”
Mare Do Well is drawing closer and closer, and she still doesn't show any response.
“You couldn't be Fluttershy, could you?”
Still, she only comes closer.
“Um... Rarity? This isn't funny, okay?”
Finally, Mare Do Well does something. But it's the last thing Rainbow expected: She pounces, tackling Rainbow to the ground in a flash of speed. And then she kisses her.
Rainbow's eyes go wide at the unexpected advance, but she can't argue with the pleasure of Mare Do Well's soft lips and deft tongue. She wraps her hooves around her masked admirer, pulling the mysterious mare closer for an even more heated kiss. She's amazing! (And somehow, she's all the hotter for being anonymous.)
Mare Do Well's kisses move over Rainbow's cheek and on down. The wet tongue and hot breath brushes against her neck, making her whole body tingle and quiver. She should be concerned about how fast this is going, should be wondering who's behind that mask, should be worried about who might see her making out in public ... right in the middle of this alley behind the joke shop. But she isn't concerned. She's engrossed with the way Mare Do Well's tongue caresses her, with where Mare Do Well's hooves are wandering.
Those kisses are trailing lower and lower, down her neck, down her chest, across her belly. Is she even going to stop? Do I want her to stop?
Before long, it doesn't even matter anymore. The masked mare's mouth makes its marvelous way to Rainbow's miniscule mammaries.
Rainbow actually whimpers in ecstasy as that mare gently suckles her teats, sending keen jolts of pleasure through her.
But Mare Do Well doesn't stop there. She goes lower still.
Rainbow can't believe it's happening ... and she can't wait for it to happen. One more kiss, two more, and then Mare Do Well makes that all-important contact. Only when that mare's tongue touches her does Rainbow realize just how incredibly wet she's allowed herself to become. What a sloppy mess must be getting in that mare's mouth! But Mare Do Well seems to revel in it, slathering her tongue greedily over Rainbow's slit.
Clenching Mare Do Well's head between her back legs, Rainbow gives herself over to it, barely even remembering to reign in her moans (she doesn't want to draw a crowd, after all). That mare is eating her out masterfully; gently teasing at first, and then building to an intensity that Rainbow has never experienced before.
Just when Rainbow thinks it can't possibly get any better, Mare Do Well does ... something. Rainbow's not quite sure what it is. It feels like it must involve soft lips and gentle suction, but it also feels like a swirling tongue circling and circling, and it's ... it's just—
Rainbow throws her head back and squeals as a massive orgasm rushes through her, blowing away all her self-control.
Mare Do Well pauses for just a moment, just long enough for Rainbow's twitching to die down ... and then she does it again.
Again and again it happens. Mare Do Well plays Rainbow like a flute, raising a symphony of Rainbow's yells and moans in the empty alleyway. It's a miracle that nopony comes to investigate the sounds, that nobody finds them, and still she keeps at it, putting Rainbow through more than even she can handle.
Finally, Rainbow manages to blurt out, “Stop! Stop! I can't ... I can't take any more!”
Only then does Mare Do Well give one final kiss to Rainbow's clit. She stands up, her mask dripping with Rainbow's juices, and looks down at the results of her good work: one completely devastated pegasus mare.
Rainbow struggles to catch her breath, staring up at Mare Do Well's unreadable face. After several long moments and a lot of gasping, she finally manages to ask the question that's burning in her mind: “That was... That was awesome! Who are you?”
Mare Do Well winks at Rainbow, then darts away, vanishing around a corner. The question goes unanswered.
Slowly picking herself up off of the bottom of the alley, Rainbow breathes a heavy sigh. (And not just because Mare Do Well orgasmed the very breath out of her, although that does have something to do with it.) She has a conundrum now: Which of her friends did she just fuck?
It couldn't possibly be Fluttershy – she would be too shy to do something this bold (or was that why she needed the mask?) Twilight wouldn’t try anything like that – she's made it very clear that she has no romantic interests among her friends (or is that just a front she needs to keep up now that she's a princess and her love interests are political ... then she would need a mask!) Certainly honest Applejack wouldn’t sneak around behind a mask (but what if this is her way of being honest with herself when her family normally wouldn't tolerate her dating a pegasus pony?) Something this random would definitely be right up Pinkie's alley, and she does have a very talented tongue (but can Pinkie possibly go so long without talking?) And Rarity had never even worn the Mare Do Well costume before (but she is the only one who still has a costume – unless one of the others has kept theirs secretly!)
Rainbow shakes her head clear. There's no way she can think her way out of this one. It's clear that there is only one choice: she'll have to fuck her way out of it! She'll have to seduce each of her friends, one by one, to find out which one of them knows that awesome tongue-swirling thing.
Imbued with new purpose, she takes off and flies straight for her cloud home to freshen up and prepare. There's only one question left she doesn't know how to find the answer to: Which of her friends should she do first?
Author's Note
This story was chosen by my 
Patreon supporters! Every month, I take suggestions from my supporters and let them vote to determine which story I'll write next.
If there's something you've been dying to see me write, please go to my Patreon page and sign up to be part of the suggesting and voting process.
