Background: Anon is in RGREqG, and principals Luna and Celestia are sponsoring him.  That means he lives with them at their house.  That's what the "no kissing unless we're at home" line comes from.

---------------------------------

>Okay, Anon.
>Let's review.
>T-shirt that's one or two sizes too small?
>Check.
>Tight shorts without any underwear underneath them?
>Check.
>Package on full view?
>Check.
>That innocent smile you've been practicing in the mirror all week?
>You bet.
>You are Anon, and principal Celestia has been giving you an awful lot of detentions with her lately.
>And they all end in the same way: with her either molesting you or fucking you.
>Usually both, except for that one time she was clearly drunk, and the two of you spend your detention hugging it out.
>And you've seen how stressed vice principal Luna can get, so you think it's time to do something about it.
>That's why you're confronting her just a few minutes before you've got another "detention" with principal Celestia.

"Shes keeps making me stay after class~"
>You play with the hem of your shirt, trying your best to look unassuming and demure.
>You glance up at Luna, make eye-contact, and then purposefully quickly look away.
>You even try to think of something embarrassing that you did in your life to make yourself blush.
"I mean," you purr, "I just don't know what she could possibly want from me."
>When you look back up again, you're pleased to see that Luna is a combination of concerned and aroused.
>To nobody's surprise, arousal is winning
>Thank you, Caramel, for all those stupid fucking lessons on "how to be a proper boy".
>If he hadn't been providing you with all the (admittedly fruity and mild) drinks you wanted during your lessons, you never would have even bothered showing up.
>You never used any of that knowledge until now, and thank christ you've got it.
>Because if you play your cards right, you'll have TWO principals riding your dick.
>You give the vice principal a small, unsure smile to make her feel like she's dealing with an innocent, pure-as-the-driven-snow boy from school.
"Do you think you could... maybe come with me one time? Please? I mean, you make me feel so safe when I'm with you~"
>Time to put on the doe eyes.
>Luna clutches her chest and lets out a quiet "hng~"
>That's right, Anon.
>Really lay it on thick.
>[spoiler]Like your dick.[/spoiler]
>[spoiler]I'm sorry.[/spoiler]
>"W-Well, Anonymous, I-"
"Oh, vice principal Luna, please just call me 'Anon'."
>You give her your best toothy grin.
"That's what all my friends call me."
>Luna returns your smile, and her shoulders slump as she relaxes in your presence.
>"Well then, then how about you drop the 'vice principal' bit and just call me 'Luna'? That way we're even."
>YES
>A teacher is insisting you call her by her first name.
>All you need is for her to sweep all the books and pens off her desk and then sit on it for this situation to start looking like some of that teacher-student porn you used to watch back on Earth.
"Okay, Luna. Thank you so much~"
>Luna bites her lower lip, but you don't think she knows she did it.
>Now all you have to do is to get Luna to walk in on Celestia slipping her hands down your shorts, and you'll have a hot threesome in the bag.
>God, you love this weird, gender-role reversed world.
>If it's not the students who refuse to wear bras, it's the perverted female teachers who are chomping at the bit to fuck their students if they can get away with it.
>And boy, are you willing to let these two sisters get away with it.
---
>Luna smiles at you and leaves the classroom, gesturing for you to follow her.
>"Of course, Anon," she says with a smile, "Let me just get something from my car first, alright?"
>You nod cheerfully and shift from your heels to your toes.
>You know from experience (read: ANOTHER hour in front of the mirror) that this makes your junk bounce juuuust enough for it to be noticeable.
>To your delight, Luna's eyes dart down to right around penis-level, and then up to your face (you guess to make sure you didn't see her looking).
>You don't say a word or give any indication that you noticed, and after a brief moment, she's back to giving your groin quick, fleeting glances.
"Okay, Luna," you chirp, "Come back soon, okay?"
>"Y-Yeah," Luna mutters, eyes still darting to your crotch, "I'l c-cum REAL soon..."
>Luna seems to catch herself staring and jerks her head in another direction.
>Coughing into her fist awkwardly, Luna spins on her heel and marches out the front doors of Canterlot High.
>You think you have just enough time to get "comfortable" with Celestia before Luna comes back and goes into her and Celestia's shared office.
>Waiting no longer, you knock on the principal's door and then open it.
>Celestia is sitting at her desk, looking over a stack of papers.
>She looks up at you when you enter the office, and her bored expression immediately melts away and reveals much more pleasant one.
>A sly smile spreads across her face, and her posture immediately relaxes at the sight of you.
>"Ah," she sighs, "Mister Anonymous. Here to report in for your detention?"
>You just nod.
>Her smile smoothly turns into a grin, and she slides up from her seat, making her way around the desk.
>"I'd like to say that I'm surprised to see you show up for another 'detention' of ours, but..."
>She looks you up and down, from head to toe; drinking you in and undressing you with her eyes.
>"...there are a lot of things I'd like to say."
>Chuckling, she slowly walks over to you, hips swinging and clearly enjoying every moment.
>"Nice shorts, stud," she purrs, "Is that for me?"
>On a side note, these shorts are SO uncomfortable.
>They're riding up your ass and your junk is pressing uncomfortably firmly against the seam.
>But this will be worth it.
>You just grin at her.
"Maybe. Do you see any other principals in here?"
>She bites her lip.
>"Such a tease."
>When she finally reaches you, she kneels down in front of you; experience has taught you that this is so that she has an easier time reaching any part of you that she wants.
>C'mon, Luna.
>You've gotta time this perfectly.
>If it's too early, Luna won't realize that Celestia has been stranger-dangering you and then NO sex will happen that day.
>Too late, and you'll be balls-deep in Celestia and unable to keep on spinning that "I'm just an innocent little boy who needs a big strong Luna to protect me" persona.
>Celestia's eyes lock on your dick, which has begun expanding at the thought of a threesome with her and Luna, and a throaty chuckle reaches your ears.
>"I hardly think I can be blamed for doing this, you know. You waltz around my school wearing those tight clothes of yours-" she stares into your eyes with a mock-glare "-and don't think I haven't noticed the lack of underwear, too. In fact, I think I put up an admirable resistance before I started calling you to my office."
>Celestia gently cups your bulge over your shorts, hefting your cock and balls and weighing them in her hand.
>"What class did you just come from, Anonymous? I need to know which grade I'm going to turn into an 'A'."
>She takes a deep breath in through her nose and shudders, planting a shaky hand on your shoulders to center herself.
>Her face begins to darken as a blush overtakes her features.
>The hand on your package slides away, and then slowly begins to slide down the front of your shorts.
>Your cock twitches as her warm fingers begins to wrap around it.
>You barely manage to hold back a moan as Celestia slowly pumps your hardening cock.
>Fuck.
>FUCK.
>Where is Luna?
>How long does it take to get your stuff from your car?
>"Eager as ever, aren't we?" she asks breathily, practically purring, "Well, why don't you hop up on my desk and we'll get to-mmph!"
>You've got to stall for time.
>If you let this go into full-on fucking, then Luna will be too angry at Celestia for "taking advantage" of you to even CONSIDER having sex with you.
>Before Celestia can do anything, you lean forward, cup the older woman's cheeks, and plant a kiss on her lips.
>Celestia's eyes snap open at the unexpected contact and her hand stops moving, but after a moment she pushes you away.
>"H-Hey, now," she stammers, "We agreed no kissing unless we're at home, alright?"
>The confident principal is now as nervous as a school girl.
>"Luna could show up at any mome-"
>KNOCK KNOCK
>CREEEAAAAAK
>>"Celestia? Anon? Are you there?"
>Before Celestia can desperately try and make it seem as though she ISN'T molesting an underage student and the boy she's letting stay at her house, you tighten your grip on her face and pull Celestia in for another kiss.
>>"Hello? Anon requested my pre-CELESTIA?!"
>You break away from the kiss with a very wet, very loud "mwah!", and you're pleased to see a saliva trail leading between your mouth and Celestia's.
>Just like from your Japanese animes.
---
>You back up into Celestia, who wraps her arms around your front.
>Partly a protective gesture, and partly because she wanted something in between her and her angry sister.
>>"Celestia!  I cannot be-LIEVE you!"
>"L-Luna!  I... I swear, i-it's not what-"
>Luna cuts her off, not giving her sister any chance to explain herself.
>>"It's not what?  It's not what it looks like?"
>Celestia smiles nervously and then nods.
>"It's... I have a good expl-"
>Luna stamps her foot angrily.
>>"How the hell is this not what it looks like?!  How could you do this to Anon?  He trusted us!"
>Celestia shrinks away; her once flushed face is now so pale you're actually a little bit worried that she's going to pass out.
>This might not have been the best idea.
>Luna's not done with her tirade; you can practically feel the righteous anger pouring off of her.
>>"What did you do, threaten to kick the boy out of our home if he didn't put up with your sick desires?  For goodness sake, Celestia, he's 17!"
>[spoiler]Magic is bullshit, by the way.  Whatever magic that plopped you into human-Equestria also turned back the clock for you so that you were conveniently the right age to attend this high school.[/spoiler]
>>"Is this what you've been doing when you keep him after school, Celestia?  You've been RAPING him?!"
>Celestia lets out a frustrated shriek in response.
>"Just look at him!  You've seen the way he dresses and you KNOW he sleeps in the nude!  I'm only human, Luna!  I'm not made of stone!"
>Fueled by frustration and lust, Celestia tugs your shorts down around your ankles, letting your cock pop out and bob slightly in the open air.
>"You see?!  See what I'm dealing with?!  How am I supposed to resist this cock when Anonymous is so willing to give it to me?!"
>The effect is immediate.
>Luna's face turns red and her tirade is cut short as she stares at your length.
>>"Oh, my," Luna gasps as your cock comes into view, "That's... impressive for his age."
>Celestia reaches between your leg and cups your sack from behind.
>"If you think that's impressive, Luna, then you should see how much tasty cum comes out of these balls."
>Luna licks her lips unconsciously and inches forward.
>>"But... but he can't... he's such a sweet boy.  How could..."
>Another step.
>>"How could he really want this?"
>Another step.
>Her breath hitches as Celestia begins to pump your cock up and down.
>"I dunno, Luna," says Celestia, pressing her chest against your back, "I think this thing right here-"
>She gives your cock a wiggle.
>"-speaks for itself.
>Luna doesn't look convinced; rather, she looks conflicted.
>The women in this world are almost all universally perverts, and you don't doubt for a second that Luna here is interested in learning more about your dick.
>It's every woman's dream, right?
>You've seen their porn sites; "barely legal boys" is the most frequently searched category of videos.
>Luna suddenly pulls back, shaking her head like a dog trying to dry itself off.
>>"H-He doesn't really want this!" she cries stubbornly, glaring at her sister, "Celestia, he's living with us! He's probably scared out of his mind that you'll kick him out if he doesn't let you touch him!"
>Celestia gives your cock a few good pumps and then points your pre-dribbling head towards her sister.
>Luna actually flinches away.
>"C'mon, Lulu, touch it."
>She reaches around and gently pats your chest.
>"This little slut comes to my office knowing exactly what's going to happen, and he does it anyway. You want this, right? Anonymous?"
>You stare right into Luna's eyes and nod, licking your dry lips.
>Sell it, Anon.
>Be the innocent schoolgirl.
>...boy.
>Whatever; do the thing!
>Luna approaches slowly before kneeling down.
>Her eyes never leave your cock.
>>"Y-You really want this, Anon?"
>Even as she lets her concerns about your consent be known, she slowly moves her hand forward until her palm is touching your head.
>It doesn't take long, after this.
>Luna shudders as she gives your shaft a few experimental tugs, and then almost violently throws herself away from it.
>>"Fuck it," she growls, tugging impatiently at the buttons of her shirt, "I'm going to hell anyway for touching him, so I may as well thoroughly earn my spot there."
>First comes the shirt
>Then go the pants
>And finally the panties; like most women, Luna doesn't bother wearing a bra.
>She lays down on the ground in front of you, belly-up, and holds her hands out.
>Wordlessly, you approach and lay down on top of her.
>Luna bites her lip and darts forward, pecking you on the lips.
>>"L-Look, just... just let's do this properly! I wanna make this special for you, Anon."
>Anon activates passive ability: Smooth Talker
"Luna, if it's with you, then it will always be special."
>The next thing you know, Luna has pulled you in for a kiss.
>"Luna's always been sentimental," says Celestia with a snort.
>She chuckles as she watches Luna squirm underneath you.
>"Don't you worry about breaking her, kiddo," she says jovially as she pats you on the back, "This is the first dick Luna's gotten in nearly ten years."
"Oh, yeah?" you ask as you pull out of the kiss, "And what were YOU like back when you first started giving me detentions?"
>Celestia's confident smile immediately falters, and she grumpily pokes you in between the shoulder blades.
>"Just hurry up and fuck my sister, Anonymous, before somebody realizes they forgot something in the office."
"You think we should do this at home?"
>>"No!"
>Luna reaches up and grabs you by the shoulders, pulling you down against her body.
>>"I've waited too long! D-Do it now!"
>In a word, Luna is hot.
>Her insides are like a wet furnace, so much like Celestia's and yet so different.
>She squeezes you like a vice as you slowly thrust in and out of your favourite vice principal and housemate.
>>"Anon," Luna moans, "Y-You were such a good boy!  I wasn't even sure if you had had y-your first kiss!  I didn't realize-hng!"
>You lean forward and take a nipple into your mouth, making Luna's breath hitch.
>>"I didn't' realize you were s-such a little gigolo!"
>"C'mon, Anonymous, fuck her harder."
>You feel a hand massaging your balls, making you gasp.
>"Are you gonna let her get away with that?  Calling you a gigolo?"
>You know what?
>Fuck no, you aren't.
>You speed up your pace, silencing Luna with a kiss when she starts to get too loud.
>The knowledge that Celestia is watching her sister have sex; the lewdness of this entire situation is too much for you, and you find yourself finishing much sooner than you would have liked to.
>You feel that familiar build-up between your legs, and you lament that you couldn't enjoy this for much longer.
>Well, at least until the next time you help Luna relax.
"Luna," you warn her, "I'm g-gonna cum!"
>You plant your hands on either side of Luna's head and start to pull out; you know Celestia is on the pill, but you have no idea what Luna's setup is like.
>Faster than you had expected her to be capable of, Luna's arms dart out and she wraps them around your neck.
>>"No no no, don't you dare!"
>Luna's office of powerful thighs rejects your request for pulling out.
>Luna wraps her legs around your waist, preventing you from doing anything but injecting her womb with your seed.
>She pulls you into a kiss that feels just as searing as the boiling-hot cum rocketing out of your cock and deep inside of her.
>She moans into your mouth and bucks her hips, her orgasm washing over her.
>You lay there for a few seconds, each of you catching your respective breaths.
>Maybe this wasn't such a bad idea.
>Maybe your plan to have a threesome was pretty okay.
>Does it count as a threesome if you have sex with one woman while the other talks dirty and touches your balls?
>You know what?
>You don't really care right now; not while you're enjoying the afterglow.
>Celestia pats your ass, and you look at her over your shoulder.
>She silently jabs her thumb at the clock, and you realize you've been here after school for nearly a whole hour.
>"C'mon, kiddo," says Celestia quetly, "It's time to get going before the janitor gets suspicious."
>You nod in agreement.
"I get you. The whole, 'I spilled yogurt all over my pants' trick only works once."
>Celestia barks out a laugh.
>"You used yogurt?" she giggles behind a hand, "I told her it was sour cream!"
>You can't help but join in her laughter, imaging what the janitor must think of you two by now.
>Luna moaning beneath you brings you back to the present.
"Well, we can talk about tricking the janitor later. I think it's time we headed home, right?"
>You pull out of Luna's pussy with a wet -pop-; a river of cum flows out of Luna's snatch in your dick's wake.
>Celestia whistles appreciatively as she peers down between her sister's legs.
>[spoiler]l-lewd[/spoiler]
>"I sure hope you're on the pill, Lulu."
>Luna just blinks groggily at her sister.
>>"The what?"
>And then her eyes widen.
>>"Oh.  Whoops."
>OH.
>WHOOPS.
---
>You are Anon, and you are now resting at home with Celestia and Luna.
>You're wearing a bathrobe (a bit frilly, but that's all they had in the men's section) and enjoying a cup of hot chocolate; Luna and Celestia are doing the same, only their bathrobes are a bit nicer than your are, and you know for a fact that their hot chocolate has a bit of liquor in it.
>Currently, Luna is snuggling against your side, letting you rest your head on her shoulder.
>>"I didn't mean it when I called you a gigolo, Anon."
>You sigh and take a sip of your hot chocolate
"I know, Luna."
>Luna hugs you to her chest and strokes your cheek.
>>"I'm sure you were just a little angel before my sister got her hands on you. Oh, you said you felt safe around me!"
>She nuzzles the top of your head and presses a kiss onto your forehead.
>>"Oh, no, we've corrupted an innocent boy!" moans Luna, sounding distressed, "D-Don't worry, Anon, I promise we'll take responsibility, okay? Did my sister steal your first kiss?"
>The next thing you know, you're suffocating in tits.
>>"Oh, no! What if I'm pregnant! I-I'm having his child out of wedlock! Oh, Anon, I'm so sorry! Your father will never forgive me!"
>You try to relax and enjoy your prison of breasts while Luna rambles anxiously.
>Such is life for Anon.
>[spoiler]They took responsibility.[/spoiler]