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Introduction:

Brittany and her older sister Sarah have always been close, but thanks to their dog Cooper they're about to grow a whole lot closer!

Technically the whole family adopted Cooper, but from an early age it became apparent that he was Brittany’s dog. He answered only to her call, slept at the foot of her bed, and spent every waking moment he could right by her side. Naturally Brittany’s sister Sarah was a little jealous, but in time she simply smiled at the dog’s antics. It certainly wasn’t like Cooper meant to offend her, and the time the dog left her alone gave her more time to attend to her studies.

At 21, Sarah was bookish in both character and appearance, her quiet demeanor appropriately matched by her short cut blonde hair and plain, conservative glasses. Her usually flat face would occasionally morph into a subtle smile at an amusing anecdote, but she rarely laughed aloud or made humor of her own.

Even Sarah’s body seemed to reflect her aura. She was deathly pale and thin, almost painfully so, and those who had never seen her daily workout might deem her fragile. The rigid routine of this workout kept her body toned and her butt tight from many brisk jogs, but try as she might couldn’t enhance her small breasts through any exercise. Sarah rarely stood out in a crowd, but she was content this way. Few bothered to bother her.

Her younger sister was a different story. It would be simple to say that 19 year old Brittany was Sarah’s polar opposite, but this wasn’t entirely true. Both girls were relatively introverted, but Brittany’s face was more relaxed and expressive, and she opted for contacts over restrictive glasses. Her bright laughter often came in bursts, and when she was relaxed conversation came naturally to her. She preferred freedom and music to her sister’s more studious approach, often finding joy in the simple parts of life.

Brittany kept her flowing blonde hair much longer than Sarah, and both her hair and her skin tone were slightly darker than her milky white sister. While Sarah was average in height, Brittany stood a few inches taller, almost brushing six foot. Brittany often skipped her somewhat haphazard workout routine, and while not fat was far from the twig her sister was. Her thighs and butt were ample and shapely, attracting many a glance from admiring men. Her chest had also filled out nicely with age, giving her a decided advantage in that respect over her older sister. Though the two sisters looked similar in the face, their body types were quite different. Men who desired smaller, petite women would often prefer Sarah, while those who enjoyed a curvier girl opted toward Brittany.

Despite their differences, both girls acted a lot alike. They dressed conservatively, seldom dated, and didn’t sleep around. Outwardly, they projected a picture of purity and innocence, a by the book definition of proper young women. But underneath this thin facade lay the reason for Cooper’s canine affinity toward Brittany. A careful observer would notice him hump her leg far too often for a normal German Shepherd pup, and he often pawed at her and whined, as if yearning for some sort of attention that she wasn’t giving him.

The explanation for the dog’s behavior was Brittany’s dirty secret. From early in his life Brittany had experimented with Cooper, jerking and sucking on his little dog cock and encouraging him to lap at her dripping pussy. What had started as a horny teenage whim had turned into an obsession, and Brittany and Cooper played at every opportunity.

Over time, Brittany developed a system of sorts for when she’d explore with Cooper. She was usually cautious and careful, only playing when the house was empty, but occasionally she’d take risks when horniness overwhelmed her. She also found she was able to keep Cooper from getting too wild by sending him with Sarah on her jogs, and Sarah seemed to appreciate the company.

On one particularly fateful day, Brittany found herself alone in her house. Her parents were away for the weekend, and Sarah had elected to go out for the day with some friends. As soon as Brittany felt confident her parents weren’t going to return for something they’d forgotten, she excitedly stripped off her clothes, enjoying the feeling of the cool air on her nude body and hardening nipples. Cooper seemed to sense what was unfolding, and as Brittany flopped down on the floor and spread her pussy wide the German Shepherd was already in position to eagerly lap away, covering everything from the bottom of her slit to her blonde landing strip with his large tongue. Brittany threw back her head and moaned, more happy than ever to be alone. Even the closest neighbors wouldn’t hear her unless she screamed bloody murder.

As Cooper continued to lick, Brittany noted his growing red rocket emerging out of its sheath. Reaching out, she was just able to grasp it and give some encouraging pulls. Cooper had grown a lot as of late, and the small dick Brittany had once barely coaxed out of its sheath now grew to a full adult sized member. She admired the intricate veins running up and down the shaft as she stroked and eyed the bulging tip. Stretching out her head, Brittany awkwardly sucked Cooper off while still getting the attention to her pussy, enjoying the pleasure in her loins and the slightly salty taste filling her mouth.

A sudden cramp from the awkward position forced Brittany to reconsider her strategy. Regretfully she pushed Cooper and his delicious dog cock gently away and shifted from her sitting position to down on her hands and knees. Then she gingerly stretched her right leg out behind her to relieve her aching thigh muscle. Although Brittany was unaware of it, this stretch put her in the perfect position for doggystyle, a fact which did not escape the notice of her excited dog.

As she brought her leg back to its resting position, Brittany suddenly felt paws on her back, and surprising strength forced her head toward the ground and her ass into the air. Before she was fully cognizant of what was happening, Cooper had positioned his paws on her thick ass, and with unexpected accuracy maneuvered his throbbing dick into her snatch.

Brittany gasped, frozen by shock and pain as the dog began to thrust into her tight pussy. This wasn’t the first time Cooper had attempted to mount her in some capacity, but it was the first time he’d had any degree of success. And no amount of masturbation or dog tongue had prepared Brittany to be penetrated so suddenly, much less by a thick German Shepherd schlong.

Grimacing in pain, she tried to pull herself away from Cooper, but the combination of her subservient position and cramped up leg made the maneuver all but impossible. Panic began to overwhelm Brittany, her rising feeling of dread matched equally by Cooper’s excitement as he pumped faster and harder.

Suddenly Brittany felt an incredible swelling inside her, sending shooting pains up and down her body. To her horror she realized that Cooper had already knotted her, making escape strictly impossible for the time being. Brittany was now Cooper’s bitch.

Tears of pain began to leak down Brittany’s face, and out of her mouth flowed screams and sobs. She swore particularly hard at her own cunt, which felt as if it was being torn apart. Worst of all, Brittany knew from her previous experience playing with Cooper that it would be a while before he was finished.

Unbeknownst to Brittany, this was about the time Sarah arrived back home. Her plans for a fun day out had fallen through, and she entered the door thoroughly miffed at her friends. These small concerns were shattered as she heard the sound of Brittany’s pained cries filling the house, chilling Sarah straight to the bone. She raced up the stairs to Brittany’s room, not stopping to brace herself before throwing open the door in panic.

The sight that greeted her eyes did little to alleviate Sarah’s terror. Brittany was completely nude and covered in sweat, her long blonde hair disheveled and falling wildly about her. Brittany’s whole body shook with pain, and she remained crouched on the floor with Cooper’s enormous dog cock clearly deep inside her. Tears streamed down her face, and in her agony she didn’t even notice Sarah’s presence.

“What the fuck?” Sarah let out, uttering a rare curse as she gazed in a mixture of horror and amazement at the scene before her.

Brittany’s head swiveled around, her face blushing with deep embarrassment almost worse than the pain. “I’m… so sorry,” she choked out between guttural cries.

Sarah had no words, but came to her senses enough to take action. She moved toward Brittany and grabbed Cooper, fully intending to pull him off her younger sister.

“Stop… don’t,” Brittany managed, struggling to make coherent phrases. “Stuck… has to… finish.”

Brittany had done enough research online to know that trying to remove Cooper’s knotted cock would only make matters worse. And though Sarah didn’t understand the anatomy of her sister’s condition, the message was clear enough. There was nothing she could in the moment to help Brittany.

Sarah considered leaving the room entirely, but something deep in the pit of her stomach kept her from running away. Despite her shock and a level of disgust with her sister’s actions, she loved Brittany more than anything and wasn’t about to abandon her in a time of need. Sarah settled by Brittany’s head, gently stroking her hair and trying to calm her. It had occurred to Sarah that Brittany’s screams might be loud enough to attract attention from others in the neighborhood, and the last thing she wanted for her sister was further embarrassment. However, Sarah’s pleas for Brittany to calm down and breathe went mostly unheard, her only response a continued scream.

“I’m… sorry.” Brittany let out again between groans. Sarah looked in her sister’s eyes, overcome by pity in place of her initial disgust. And gradually, there arose another feeling. Deep within herself, Sarah felt a primal arousal. Her sister’s nude, dripping body was causing her own pussy to leak, and the animalistic pounding Brittany endured only heightened the sensation. Sarah’s nipples began to harden and she had to resist the urge to massage her own small tits. She’d known for a while that she had a thing for girls, but her own sister? These feelings were new, and far more powerful than any she’d ever experienced.

Drawn partly by shock and mostly by instinct, Sarah slowly leaned in toward her sister, causing Brittany’s eyes to widen as a shout died in her throat. In a moment that seemed like eternity their lips met, kissing with a passion neither girl had experienced before. In an instant Brittany’s body relaxed, her mind far from the dog inside her as she hungrily kissed Sarah back, their tongues tangling in a wet embrace. There was almost a desperation to their meeting, built up by years of tension that neither had ever acknowledged

The relaxation brought on by the kiss was exactly what Brittany needed, and though she was still in significant pain, pleasure began to seep into her from her abused pussy. She moaned deeply into Sarah’s mouth, a sensual expression rather than a panicked one. Sarah moaned back, her hands reaching up and cupping Brittany’s face as their mouths melded together.

Eventually the need to breathe broke them apart, both girls gasping and breathing hard. For a few seconds they couldn’t even look at each other, overcome by a flood of different emotions.

“Well that helped,” Brittany said simply, her voice less strained than before.

Sarah looked into her sister’s eyes with a smile. “Then we’d better not stop,” she replied. Their lips met again, and Brittany desperately wished she could wrap her arms around her slender sister as they kissed.

Growing ambitious, Brittany’s mouth soon moved elsewhere, kissing and licking Sarah’s sensitive ears and neck. “Oh Brittany,” Sarah whispered, her senses heightened like never before. As Brittany continued moving lower toward her collarbone Sarah interpreted the unspoken message, quickly pulling her shirt over her head and unclipping her simple white bra. Her small tits greeted Brittany’s eyes, and Brittany’s mouth followed soon after, latching onto a nipple as she sucked and nibbled. Sarah threw back her head and voiced her approval, groaning just as Brittany had when Cooper licked her slit.

Unabashed and unable to contain herself any longer, Sarah thrust a hand down her jeans to rub her clit. Brittany’s already stuffed snatch continued to feel better and better as Cooper shifted slightly inside her, and soon the room was filled with a chorus of moans from both girls, complemented by the sounds of a panting dog and Brittany sucking on Sarah’s succulent breasts.

All at once Brittany felt a powerful feeling welling up deep inside, and she was unable to announce her orgasm before it washed over, overwhelming her. Sarah didn’t require an explanation as Brittany’s eyes rolled back into her head and she became incapable of doing much of anything. Sarah was more than happy to simply enjoy the sights and sounds, and took the opportunity to strip off her jeans and panties, giving her fingers easy access to her dripping cunt.

After a couple earth-shattering moments Brittany recovered from her orgasm, her knees weak but the dog still firmly inside her. She looked up at Sarah, face flushed with embarrassment but a smile on her face.

“Enjoying yourself?” Sarah asked teasingly as she continued to furiously rub her own pussy.

“Even more than I thought I would,” Brittany replied, leaning in and kissing Sarah. She pulled away quickly after, a different thought already on her mind.

“Bring that pussy over here and let me show you something Cooper taught me.” Brittany motioned with her head, indicating for Sarah to position her pussy just below her mouth.

“Do your worst,” Sarah responded, moving into the proper position and spreading herself wide with her fingers.

Brittany happily obliged, burying her nose in her sister’s wild blonde pubic hair as she licked and explored with utter abandon. Her experience with Cooper lent knowledge to her efforts, and she focused on the areas she’d often guided the pup’s eager tongue toward.

“Oh yes Britt, don’t stop,” Sarah moaned, lying back flat on the floor. Her already wet slit leaked even more of its juices, and Brittany was all too happy to lap them up. Sarah gently humped into her sister’s face, driving Brittany’s tongue deeper and deeper inside her.

Despite Brittany’s inexperience, Sarah’s excitement more than compensated. Before long Sarah let out a sharp gasp. “I’m cumming!” she exclaimed, for the first time in her life announcing her orgasm aloud. Even more juices gushed into Brittany’s mouth, and Sarah’s orgasmic screams almost rivaled Brittany’s earlier screams of pain.

Sarah collapsed on the floor, and as she did the strings of fate fell into place for Brittany. A few seconds later Cooper let out a whimper, and Brittany felt a hot spurt deep inside her womb. This was followed by an explosion as Cooper drained his swollen canine balls into her waiting cunt, shooting strand after strand. Thin, runny dog cum dribbled past his cock as he filled her to the brim, and as he finally retracted his member the excess practically flowed out onto the ground.

Now it was Brittany’s turn to collapse, exhausted and her pussy abused beyond belief. Sarah quickly recovered sufficiently to crawl over beside her sister, giving her thick butt a playful slap and gently rubbing her back. As Sarah surveyed Brittany’s cum soaked snatch, she found herself inexplicably drawn toward it. To both girls’ surprise, she bent down and gave it a generous lick, gathering up a mouthful of dog jizz as she did. Lying down beside Brittany, she then kissed her deeply on the mouth, the two finally wrapping their arms around each other as they swapped the thin cum. After several minutes they pulled apart, swallowing what remained of the load and shakily sitting up.

“You know, I’ve tasted his jizz before, but it’s never been quite that good,” Brittany said with a slight laugh.

“Glad I could help,” Sarah responded. Both girls laughed, reveling in their new found freedom and sexuality.

“I’m sure I can find a way to thank you for… helping me survive that,” Brittany said, glancing over at Cooper lying exhausted on the ground.

“Yes, I’m sure we will,” Sarah replied, pulling her sweet sister into a warm embrace. “Now let's go get cleaned up. We can deal with this mess later,” she said, gesturing to the cum stained carpet and exhausted dog. The two got up and started walking to the shower, Brittany limping from the abuse as Sarah helped her along.

“You know, Mom and Dad have been complaining for years about us using all the hot water. Maybe if we shower together they’ll finally leave us alone,” Brittany said, her tone joking and suggestive at the same time.

“Maybe. But we’d have to actually you know… shower and not spend the whole time making out,” Sarah replied with a wink. Both girls laughed as they entered the bathroom.

“Well, since they’re not here today I’m sure they won’t mind if we waste a little,” Brittany said with a sly smile. The two girls kissed and embraced once again as Sarah turned on the shower, both blissfully unaware that their journey was only just beginning.

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