Sundown
Princess Luna lay atop her sheets, facing toward the opulent headboard of her horse-sized bed. Her legs were tucked beneath her body in cat-like fashion, her voluminous tail hanging off the end of the bed and swishing back and forth.
Her door had been left open and she was rather into her reading, thus failing to notice her sister enter the room behind her.
The elder princess had come to inform her that she was expected in the greeting hall, but the sight of her sister’s supple flanks and the cute, exited motion of her tail constituted a change in plan.
Celestia crept up behind her younger sister, admiring the cosmic splendor that shone through her mane and tail. She savored Luna’s plump purple behind resting upon her fetlocks, and in her mind traced the slender curve of her back.
Every so often she caught a glimpse of her puffy little pussy, tighter than a vice, set below the ring of her anus.
Celestia gently lowered her muzzle and waited for the tail to swing wide, catching it with her magic and swiftly plunging her tongue into the tight, delicate ass beneath, pressing her face against her sister’s ass.
Luna shivered from the base of her spine to the tip of her horn, letting slip a girlish yelp that made Celestia tense up, her every muscle responding to the overwhelming power of her little sister’s cuteness.
Luna tensed as well, struggling to look behind her. “Who-“ she began, but was cut short when Celestia braced her fore-hooves against Luna’s behind, pressing firmly into the soft flesh and stirring it up as she pulled her head back.
“S-Sister?” Luna managed, her breathing heavy. Celestia, still holding her tail hostage, yanked it high, making her gasp and slam shut the cover of her book on accident.
Celestia leaned in again, this time flicking her sister’s clitoris with her tongue, turning Luna’s gasp into a staggering sigh.
Just as Luna’s moaning reached its peak Celestia stopped, releasing Luna’s tail and letting it fall, twitching occasionally as the hairs grazed her overly sensitive sex.
“Why would- Why did you...” Luna was too embarrassed to finish.
In truth, it had taken quite a bit of willpower for Celestia to pull out when she did, but it was worth it to see her sis trembling on the edge, practically pleading but too bashful to say it outright.
Her hind legs had slipped out from under her and hung over the edge of the bed, revealing her swollen teats pressed against the mattress.
Celestia grabbed her tail again, this time pinching the tip and using it to gently dust the bottoms of her hooves. The reaction was impressive and rather satisfying, her sister crossing her hind legs and squealing.
Celestia giggled as Luna buried her face in her pillow, trying to stifle her voice and hide her embarrassment.
That one electric pulse was enough to break the dam. Celestia watched with curiosity as Luna’s pussy twitched, projecting clear nectar onto her own, outstretched hooves, then spilling the rest onto the bulge of her mammaries.
Luna decided that she would be angry with her sister for a while, only... later. Having endured her punishment, she somehow felt that she had not yet had enough, and was relieved to see that her sister felt the same.
Celestia had taken a step back to get a better look at her adorable sister, smiling as she watched her ear twitch, the last vestiges of her orgasm slipping away.
‘Flip over.’ said Celestia softly, nudging Luna’s rump with her muzzle.
‘You jest. Surely you do.’ said Luna, looking over her shoulder. Her face was burning and she suddenly felt thirsty, but she managed to keep her voice level.
Though her big sister’s face bore a hint of a smile, Luna could tell she was quite serious, not that she truly doubted it.
“Fine.” she said, using her magic to return the book to the shelf. She twisted her heavy body, keeping her wings close as she shifted awkwardly.
When she was on her back, fore-hooves hanging like the paws of a begging dog and hind-legs spread apart, high in the air, she found that she could hardly stand the embarrassment of her sister gazing upon her. She covered her eyes with her hooves while Celestia shifted her gaze down to her bulbous teats.
‘You are adorable, dear sister.’ said Celestia, lowering her face to suck gently on one of Luna’s nipples. Luna peeked out at her sister just as her tongue made contact.
Though humiliating, the feeling of her sister sucking softly at her breast was strangely comforting. She looked on as Celestia alternated between them, softly pressing into them with her teeth and pinching the nipples as she pulled away.
This went on for a while, until Celestia decided it was time to try something else. Using her magic, Celestia once again grabbed the end of Luna’s tail, sending it drifting over to her mouth. “Bite down, sister, and pull. I want to see it threaded between your breasts.”
Luna did as she was asked, and Celestia delighted at seeing her sister sprawled out, pulling her tail taught as it ran like a river of stars down her belly and between the valley of her tits.
“Breathtaking.” said Celestia, in such a way that it almost made Luna feel proud, if only for a moment.
“Now, let’s try this.” Celestia retrieved her sister’s tail. “Bring your legs together.”
Luna obeyed, drawing her four hooves together above her belly, watching as Celestia wrapped the length of her tail around them, tightly binding them together with a knot.
“Wait. What-“ she began, struggling against the makeshift bonds.
“I have some business to attend to, but I shall send somepony to fetch you before long. I wonder if you shall be able to free yourself before then.” Grinning, she left her furious sister to strain against her bindings, not bothering to close the door.