“Isabel!”

Startled at the sound of her name being called, Isabel turned and looked back through the throng of customers in the shopping mall. The voice had definitely been female, and it wasn’t long before she spotted its owner approaching her.

“I thought that was you,” Sadie said with a grin as she drew near. “How’ve you been? It feels like forever since we’ve seen each other...”

Isabel smiled back. “I’ve been really good! It’s great to see you.”

The red-haired girl peered at the paper bag in Isabel’s left hand. “Ooh, been doing some shopping? What you get, if you don’t mind me asking?”

Looking around furtively, the slender blonde girl stepped closer to Sadie before answering in a low voice, smiling shyly. “Just some, uh... fun stuff the Professor wanted me to get...”

Sadie raised her eyebrows excitedly. “Fun stuff, huh? Really clever euphemism, Izzie!” she giggled.

Isabel blushed. “It’s not what you think - it’s not exactly, y’know, sex toys.” The last two words were as sotto as she could voce them. “We’ve already got plenty of those. But the Professor wants to do pet play, so she had me buy some stuff to make me look like a kitten.”

“What, like cat ears, fluffy tail, that kind of thing?”

“Yeah, and a kitten onesie...” Her blush grew yet more pronounced. “And, uh, a bowl. An actual cat bowl, for me to drink out of.”

Sadie laughed uproariously. “Oh, that’s amazing! I’d forgotten the Professor’s wicked sense of humour. Aw, and look how embarrassed you are! You remember who you’re talking to, right? There’s not a lot you could say that’d shock me, or make me judge you!”

Isabel knew this was true, but couldn’t help squirming a little anyway. She was sworn never to reveal the arrangement between herself and Professor Reed, and as such, most of the world was under the impression that she was nothing more than Reed’s TA. She’d got into the habit of keeping up the pretence, so it was difficult for her to adjust to someone who knew that she was really the Professor’s slave. To be fair though, such people were few and far between - as far as Isabel knew, only three people knew the truth, including Sadie.

And Sadie was hardly in a position to judge - she was a slave too. Adam, one of Reed’s students, had made a fortune by regularly renting out his scarlet-haired submissive to friends and acquaintances. He’d let the Professor borrow Sadie in exchange for better grades, up until Isabel had become the Professor’s slave. Since then Reed had lavished her attention on a very grateful Isabel and made less use of Sadie, particularly since Adam went home for the summer and took the vermilion-haired vassal with him. It must have been at least four months since Isabel had seen her sister slave.

Sadie got out her phone and checked the time. “Hey, have you got time to catch up? I just popped over here to get a coffee from that nice new place - you could join me. I don’t have to be back home for another hour and a half, Master’s busy til then...”

Isabel chewed her lip and got out her own phone. “I’ll have to check with the Professor.” Reed was teaching a class at that moment, and would be for at least another couple of hours, so it wasn’t as if there was any hurry. Still, Isabel knew it wasn’t appropriate to do something without the Professor’s permission.

She sent a quick text: Professor, I just ran into Sadie - may I get coffee with her please? I live to serve you xxx

Thankfully, the Professor sent a reply in less than a minute - now that Sadie thought about it, she might be between classes right now. Of course you may, my dear - have a great time! You’re a good girl x

Isabel felt warmth embrace her like a hug. Obeying the Professor in all things had become a way of life for her in the past six months, but she still got that surge of delight and pleasure every time she did as she was told - or, as in this case, when she was permitted to do something. She hoped that sensation never went away.

She grinned at Sadie. “The Professor says I can come with you!”

“Fantastic!” the more experienced slave replied with a broad smile. She hooked her arm through Isabel’s and began to lead her through the busy mall.

***

The new coffee shop, Autumn Warmth, had a rather rustic vibe. Lots of wood panelling on the walls, and plenty of wooden tables - or at least, they looked wooden. They might’ve been plastic painted to look like wood. Sadie and Isabel both decided to take it all at face value - neither of them wanted to break the illusion, enjoying how the place evoked feelings of being in a cabin in the woods rather than in a mall.

After collecting their drinks from the pretty brunette barista - with whom Sadie couldn’t help flirting - the two girls made their way to one of the tables. Isabel had bought an espresso, while Sadie had opted for a pumpkin spice latte, which she had already begun to sip.

“Mmm, that’s really good,” she sighed. Rather than sitting opposite Isabel, she sat next to her on the same long, soft, burgundy chair, her arm and hair brushing against Isabel. The blonde girl felt a thrill go through her at the contact.

“I, um, I’ve been meaning to check this place out since it opened,” she commented, trying to ignore the little ripple of arousal. “I hear Autumn is the owner’s name... D’you think that was the girl who served us?”

Sadie chuckled. “No, I don’t think so. In my expert opinion, I’d say that girl’s a college student trying to earn some extra bucks, not a small businesswoman who wanted to fulfil her dream of opening a cosy cabin-in-the-woods-themed coffee shop. Also, I read her nametag.”

Isabel smirked. “While you were checking her out, you mean?”

“Naturally,” Sadie said with a smile, completely unabashed. “She didn’t seem to mind - if anything, I think she was trying to give me a slightly better view! Anyway, her name’s Natalia.”

She turned slightly in her seat so she could look at Isabel more directly, and the diagonal direction of her body brought her legs into direct contact with her friend’s. She made no effort to move them, and Isabel had nowhere else to put them. She bit her lip to suppress a whimper at the further physical contact. If Sadie only knew what she was doing to her...

She probably does know, Isabel realised, grinning. She’s such a minx sometimes!

“So, how’ve you been lately?” Sadie asked, her face a picture of sincere interest. “I take it things are going well with the Professor?”

“Uh, yeah,” Isabel nodded. “I just started my last year as a grad student. I’m still working as the Professor’s TA, as well as being her slave, so that takes up a lot of my time - but she always makes sure I have enough time to carry on my studies. She even helps me and gives me advice if I need it.”

“Wow, that’s so kind of her!”

Isabel beamed. “I know, right? She doesn’t have to do that. She doesn’t even have to let me stay in college. If she asked, I’d drop out and concentrate on just being her slave. But I like that I get to continue my education as well.”

“Good for you! I didn’t get the same option - Master had me drop out so I could serve him full time.”

Isabel noticed a strange look in Sadie’s eyes - not sad, as such, it wasn’t deep or pronounced enough to be described as that. She’d call it more... wistful?

“Do you wish you had got to carry on?” she asked. “Do you miss it?”

Sadie shrugged. “I mean... a tiny bit? I did once think my life was gonna work out in such a different way... But that was before I realised being a slave was my true calling.” She wrinkled her nose. “Yuck. ‘True calling’? Who do I think I am?”

Both girls laughed.

“So yeah, I guess I get little pangs of nostalgia every now and then,” Sadie continued. “But I’m more than happy with my life as it is now, and how it’s gonna continue to be. I mean, why would I want to do anything else when I can be a slave?”

Isabel nodded fervently. “Exactly. I totally get what you mean. I can’t imagine living my life any other way now...”

“Yeah, getting a diploma would feel great, but not as great as lying on my back with Master’s feet on my face!”

“Mm,” Isabel sighed. “Or having to keep tidying up messes the Professor deliberately makes just so she can watch me bend over and pick stuff up.”

“Or standing behind his chair at attention, waiting for maybe an hour at a time for him to give me an order...”

“Or getting force-fed her pussy, and not being allowed to wash my face after...”

They both gazed into space, lost for a few moments in a series of delightful memories and fantasies.

“Why don’t more people do it?” Sadie wondered. “Surely we can’t be the only two who feel this much ecstasy, who get so much out of doing it...”

“Hmmm.” Isabel contemplated this. “Well, maybe we’re not. Maybe there are loads of others! But how would we know? We both keep it private - only a few people know about you, and even fewer about me. There could be a dozen other slaves in this mall right now, and we’d have no way of knowing!”

Sadie’s eyes lit up at this notion. “Oooh, maybe. Hey, a couple of them could even be in here. Maybe Natalia the cute barista has a secret other life as someone’s submissive.” She stared across the shop in the direction of the pretty brunette. “Mmm, she’d look so good in a collar...”

Isabel thought Sadie might drool at any second. Not that she could blame her.

“Hey, speaking of, where’s your collar?” she said suddenly. “I can’t remember the last time I saw you without it on!”

Sadie frowned momentarily, her hand unconsciously reaching for her bare neck. Then she chuckled lightly. “Oh yeah, I don’t wear it in public - y’know, the whole secrecy thing...”

“Oh right, sure. Silly me!”

“No, I get it, it must be weird seeing me without it. It feels weird without it! I feel kinda naked. But it’s definitely not as nice as actually being naked!” She scratched her neck with her index finger, clearly slightly agitated now that she’d been reminded of the absence of her beloved collar. As someone who also wore a collar most of the time, Isabel had some idea of how she must feel.

“Well, I’ll try not to keep you here too long! So you can get back home and put it back on again...”

“Oh, no, don’t worry about it,” Sadie laughed. “I can bear to be away from it for a little while!” She lowered her arm from her neck, her hand accidentally (?) brushing against Isabel’s chest as she did so. Surprised, Isabel couldn’t suppress a high-pitched mewl as an electrifying tingle ran across her breasts. She clapped a hand over her mouth.

Sadie raised her eyebrows. “Although, maybe I’m not the one who needs to get home!” she remarked with a smirk. “You seem pretty worked up...”

Blushing furiously once again, Isabel buried her face in her hands. “Um, yeah!”

“Must be a pain, having to wait for the Professor to finish her classes. You wanna head home and rub one out? I promise I won’t be offended!”

“It won’t do any good,” Isabel sighed. “In fact, it’d only make things worse. It’s not appropriate for me to have an orgasm today.”

Sadie frowned, while simultaneously starting to form an amused grin. “Really? How come?”

“I’m only allowed on Sundays. Or as the Professor calls them, ‘Sunday Cumdays’.”

Sadie burst out laughing, and kept going for almost a full minute. Still highly embarrassed, but unable to ignore the absurdity of her own words or her sister slave’s infectious merriment, Isabel started to giggle too.

“Oh, oh... that’s genius,” Sadie hooted, wiping tears from her eyes. “Oh, God, the Professor is just wicked. But wait, today’s Friday... And if you two have been doing sexy stuff every day since last Sunday - which, I have to imagine you have been - then that explains why you’re so -”

“Yeah,” Isabel interrupted, nodding and smiling, a slightly pained look in her eyes. “Yeah, it’s... it’s bad.”

Sadie couldn’t suppress more laughter at her poor denied friend’s expense. Isabel gamely sat there and let her get her amusement out of her system.

“Oh, man... I mean, I’ve been denied before. Master’s banned me from coming for like a day or two at a time. But a whole week?! Even he wouldn’t be that cruel.” She smirked. “Not that I’d be against it if he did want to be that cruel. That’s a fun kind of hell I’d like to try once or twice...”

“Once or twice, yeah,” Isabel chuckled. “Try doing it for three months.”

“Three months?!” Sadie squeaked. “Holy shit, what did you do to piss the Professor off?”

“Nothing! She made it perfectly clear that this isn’t meant to be a punishment!”

Sadie looked sceptical. “Well, it’s pretty punishing, though!”

“She just likes the idea of me being horny and frustrated all the time. Which I am.” Isabel drew in a deep breath, staring dead-eyed into space. “A lot. It’s not so bad near the start of the week, but by this time, all I can think about is getting off, and not being able to get off... I am literally counting down the hours until Sunday Cumday!”

“Well, I guess you can spend the whole day making up for lost time, right?”

“Oh, yeah. And the Professor usually makes it a real treat for me. She tries to get all her grading done by the end of Saturday night - with my help - so Sunday Cumday is clear for as much fun as possible. She always thinks up the most fun things to do, as well...”

“Like the kitten stuff?”

Isabel smiled. “I think that’s for tonight, actually. But she might want to revisit it, I don’t know...”

Sadie sat back in her seat and gazed at the blonde slave, clearly enjoying how frustrated she must be right now. She reached out with her index finger and stroked Isabel’s breast through her fluffy pink sweater.

Isabel screwed up her face as she tried to contain the noises of arousal desperately trying to escape her mouth. “Stoooppp,” she whined, squirming at the soft but insistent caress. She didn’t move away though - she didn’t even try.

God, I’m so whipped, I can’t even resist the whims of another slave, she thought with a smile.

***

Sadie was having a lot of fun. She always liked catching up with Isabel - the girl had a meek, shy charm that Sadie found irresistible. Plus, she was an exquisite fuck.

Catching Isabel in this flustered, barely-composed state was an unexpected treat though. It wasn’t often that Sadie got to be the more dominant of any pairing, and she took great pleasure in stepping out of her comfort zone. She made a mental note to try and catch up with Isabel on Fridays more often. Or Saturdays. Yeah, that’d be even better...

There was a sudden, insistent vibration from Sadie’s pants. Reaching into her pocket, she pulled out her phone and glanced at the screen, which showed that she had a text from her Master. Lowering her other hand from Isabel’s chest, she unlocked the phone and read the message.

“What is it?” Isabel asked.

Bemused by what she’d read, Sadie nonetheless did as she was told, just as she always did. She looked up at Isabel and said, “Arcane silver falcon.”

There was a moment of surprise on the blonde girl’s face, and then her eyes rolled back in her head and she slumped down in her seat, her head coming to rest on Sadie’s shoulder, face nestled in her long red hair.

Sadie blinked. She glanced back at Master’s text: Tell Isabel, ‘arcane silver falcon’. As she peered at her phone screen, another message came through: Don’t be alarmed, Isabel’s just having a little nap. The Prof told me you 2 were hanging out.

As usual, Sadie took this at face value. She twisted her head round to gaze down at Isabel. Wow, she thought, the Professor must really be wearing her out if she’s dozing off in the middle of a coffee shop!

A third text: Take a photo of her, and send it to me and the Prof. Then say ‘grand young Taurus’ to her. Text me back when she wakes up. Don’t tell her she fell asleep.

Still nonplussed, but as compliant as ever, Sadie immediately opened her camera app. Given that Isabel was leaning on her, she figured it’d be easiest to take a selfie of both of them. She held out her phone in front of them, and moved her face close to Isabel’s head, gazing up at the camera with her favourite ‘shy but saucy’ smile - the perfect combination of demure and provocative, with her most smouldering eyes. Then she took the photo.

She was delighted with the result. In all modesty, she thought she looked very hot and enticing - while the peacefully sleeping Isabel looked simply adorable, particularly with the tiny droplet of drool that had just slipped out of the corner of her mouth as the picture was taken. Sadie promptly sent it to her Master, and then to the Professor.

“Grand young Taurus,” she said at last.

Isabel woke with a start, slowly sitting up straight and rubbing her eyes. “Uh... what were we talking about?” she grunted, wiping away the drool on her face with the back of her hand, seemingly without even being aware of it.

Sadie struggled to suppress her smirk. “Nothing much,” she replied, “I was just teasing you about being denied and frustrated.” She quickly texted Master back: All done! I obey my Master xxx

A part of her wanted to tease Isabel even more about falling asleep, but Master had ordered her not to tell her, so she wasn’t going to. At least it was fun knowing something Isabel didn’t!

“Oh yeah, you were, you big meanie!” the blonde slave said as she yawned and stretched. “I’ve gotta get you back for that somehow...”

Sadie raised an eyebrow. “In all seriousness, I’d like to see you try! The outcome will be either hot or funny, depending on whether you did get one over on me somehow...”

“Yeah, I guess so,” Isabel chuckled. “But I have a feeling today’s not gonna be the day, is it?”

Before Sadie could answer, both of their phones buzzed within a second of each other. They exchanged sly glances - that couldn’t be a coincidence!

Sure enough, they each had a text from their respective owners - who had clearly been in contact with each other. If the timing of the texts hadn’t been enough of a clue, the fact that the messages were almost identical was even more of a giveaway.

“Oh, God,” Isabel groaned, burying her face in her hand.

Sadie fell about laughing. “Looks like you were right, Izzie - today really isn’t your day!”

***

Her eyes darting around furtively, Isabel strode in the direction of the coffee shop’s bathroom. Though she knew it was unlikely that anyone seeing her would imagine she was going in for any reasons other than the obvious, she still felt anxious, like they were going to be caught at any moment. Sadie had about a ten-second lead on her, but had already disappeared from sight.

They had entrusted Isabel’s shopping bag to Natalia, asking her to keep it safe behind the counter and not to look inside it. The barista was perfectly willing to help, although Isabel wondered if that was because she was polite and good at her job, or because she’d noticed and appreciated Sadie’s attraction to her.

The grad student quickened her pace, hurrying into the bathroom. There were three stalls, all of which were unlocked. From what Isabel could see, they were quite spacious, and as close to immaculate as they possibly could be. The door to the middle stall may not have been locked, but it was closed. She pushed it open and darted inside.

Sadie’s eyes, already blazing with lustful intensity, lit up even more at the sight of her. “What kept you?” she joked, giving her hair a provocative flick.

Grinning, Isabel closed and locked the door behind her. Without further ado, she stepped towards Sadie, seized her by the waist, and pulled her in for a passionate kiss.

They made out with closed mouths for a few seconds, Sadie’s fingers running through Isabel’s short blonde bob. As their sets of teeth parted to allow their tongues access, one of Isabel’s hands moved down onto Sadie’s round, ripe ass, fondling it gratefully, while the other slid up her back and then - slightly awkwardly - across to her front, reaching her plump breasts. Of all Sadie’s many wonderful attributes, Isabel thought her boobs were probably her favourite. She groped them eagerly, pinching the nipples. She even let go of Sadie’s butt so both hands could devote their attention to the higher vantage point. Sadie moaned softly in between kisses, her own hands tracing along Isabel’s neck and shoulders, sending electric tingles through her.

After a certain amount of time had passed - neither of them were sure how long exactly, it could’ve been thirty seconds or five minutes - their hands, almost perfectly synchronised in their movement, slid down the front of each other’s pants. As one, each slave began to finger the other mercilessly, eliciting animalistic grunts and plaintive whimpers.

In a rare forceful moment, Isabel pushed Sadie back against the wall of the stall, holding her there with the weight of her own body. This served to turn both of them on even more, and they sped up, repeatedly and rapidly impaling each other with their digits. Their eyes were tightly shut. Sadie’s head was pressed hard against the wall behind her, her mouth wide open. “Oh, oh, oh, oh...” she cried softly, again and again.

Isabel’s face was buried in Sadie’s shoulder. She was in hell - so close to orgasm, knowing there was absolutely no way in the world she could go over the edge. Not for another 32 and a bit hours anyway. “Fuck, fuck, fuck, fuck,” she grunted as she tried desperately to endure the overwhelming tsunami of arousal and the continued thrust of foreign fingers in her pussy.

There was only one way this could end. She had to make Sadie cum. And she had to do it as soon as possible, or she would probably go insane.

Acting on impulse, she bit Sadie - just a short, sharp nip on the collarbone. At the same time she reached up with her free hand and tweaked Sadie’s nipple.

That did the trick. Sadie gave a strangled cry - her efforts to keep relatively quiet and not attract attention to their amorous activities caused her to cut off her orgasmic scream almost as soon as it begun, replacing it with a stuttering squeak. Lost in the moment of release, her hand stopped fucking Isabel’s pussy and instead simply grabbed hold of it, while she hooked her leg around Isabel’s waist, just hanging onto her sister slave for dear life as she came long and hard.

Finally, she let her leg drop down and withdrew her hand from Isabel’s pants, sagging limply against the wall, exhausted but clearly overjoyed. Wiping the sweat from her forehead and face with one hand, Isabel lifted the other - the one that had been inside Sadie, and had taken the full force of her gushing orgasm moments ago - to her mouth, beginning to lick it clean.

“That... was fucking... awesome,” Sadie gasped.

“Yeah,” Isabel whimpered. She hadn’t meant to whimper, but it came out that way. “That’s one word for it...”

Sadie giggled weakly. “Oh, you poor thing! I don’t know if Master knew about the whole Sunday Cumday thing when they sent their instructions, but the Professor sure did. She must really get a kick out of torturing you!”

“She is cruel and heartless,” Isabel sighed. “I fucking love her so much.”

Sadie abruptly moved closer to her - she practically bounced, her depleted reverses of energy suddenly seeming almost completely renewed. (Isabel would love to know where she got her energy from!) She kissed Isabel once again, softly and tenderly, and then set to helping her lick her own juices off Isabel’s fingers.

***

Minutes later, they emerged from the bathroom, returning to the main area of the coffee shop. Isabel was at least four times as horny and frustrated as she was before, and was sure she looked extremely dishevelled.

Sadie, on the other hand, looked almost immaculate - you’d never have known she was coming her brains out less than five minutes ago. She must have had a lot of practice composing herself and fixing her appearance after a carnal act. Now that Isabel thought about it, she had heard that Sadie was an infamous slut even before she became a slave.

They approached the counter, where they were greeted by a cheerful Natalia, who held up the shopping bag for Isabel. “Thank you so much,” she said, taking it.

“No problem at all!” Natalia chirped. “Happy to help.”

“We really like this place,” Sadie remarked, fixing the brunette barista with her smouldering gaze.

“I’m glad to hear it,” she responded, her tone a little softer now, a slightly dreamy look in her eyes as she contemplated her crimson-haired customer. “And I actually have something for you as well...”

She held out a piece of card, which Sadie took with a smile. Isabel caught a glimpse of a series of numbers written on it, before Sadie slipped it down the front of her shirt, tucking it in her bra.

“Hope to see you again soon,” Natalia said breathily.

The redhead winked at her, before strolling away. Isabel followed close behind her.

“You barely spoke three sentences to her the whole time we were there,” she grumbled, taking the sting out of it with a sly smile. “And now you’ve got her fucking number. Jammy bitch!”

Sadie the Slave grinned back at her fellow fucktoy. “Come on, girl. Who wouldn’t want a piece of me?”