Anyway, this tale is set in my unified story Multiverse and features my android race known as Sisters. You don't need to go back and re-read my other story, this fully accessible to new readers.
Also be aware that this is a real story with a plot, so even though it lacks all sex all the time I would hope that some of you will give it a chance. I am carefully writing the story so that the reader will find themselves taken on an exciting ride where they will be unlikely to guess what might lay around the next plot twist. 
I have made an effort to avoid boilerplate exposition. Details of the Sisters and their world will be explained in an organic way at the points where you need to know them. However I will drop interesting little tidbits from time to time to give my readers hints about what might be coming next. Also, I like to inject a good element of humour into my stories so thee will be a number of fun references and inside FBC jokes.
Anyway, here are the first three chapters, I should get some more up by the end of the weekend. Comments and questions will motivate me to work faster.
Also, I am open to reader requests if you find the "action" lacking 
BTW if anyone wants to help me crank out more content helping me proofread or discussing plot ideas feel free to drop me a message, private or instant.
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Mirror Image
Chapter 1
Rolland stared at his computer screen, the test code starting to blur together in the harsh white florescent light. He needed a break, but his workstation didn't have Internet or even regular classified network access. When he was first approached about an internship opportunity at what was colloquially known as Area 51-A he thought it would be a chance to work with some of the most cutting edge technology in the world. Instead it was an endless monotony of hours trying to reverse engineer the functions of strange programs and algorithms located on remote servers. As an intern he wasn't qualified for the compartments required to directly interact with the programs, let alone know where they came from or see the hardware they were running on. Even worse was the fact that he was stuck in the middle of the desert, to even reach the nearest town was a half hour drive. This dream job was quickly becoming a royal pain and not something that Rolland believed someone of his great talent should be subjected to. He sighed, only three more weeks before the internship was over and he could go back to school.
"Hey Rolland, I need to head down to the courier office, you're the only one in here so don't leave the office without locking the door."
"Sure thing Tom," replied Rolland without even looking up at the office technical director. It wasn't like he was able to go anywhere, all of the rooms required special access. Just about the only place Rolland ever went were the bathroom and the vending machines to stock up on Code Red and Funyuns. The only relief was the lack of overtime budget which gave Rolland a good amount of free time each day back in the civilian barracks with its high speed Internet connection where Rolland could engage in his secret fantasies. Years of social rejection, poor hygiene and a lack of people skills had pushed Rolland away from the normal interest in biologic women and into the sci fi realm of androids and synthetic females. What started as a few idle conversations on forums has morphed into a large collection of movies, pictures and fiction meticulously stored and stored on several large capacity hard drives. Aside for a few tame printouts and his usual choice of t-shirt, Rolland's fetish was completely banished from his workplace. Half the reason he had taken this job was on the vain assumption that he would get to work with AI's or actual fembots, but all he got were endless programmes to test and debug.
He was just about to compile and run another unit test when he got a popup demanding a module that could only be found on the CD. Sighing and hefting himself out of his rolling chair Rolland went to Tom's office to get the disc. Passing Tom's desk Rolland noticed his team leader had failed to lock his screen, taking an idle glance at Tom's monitor made the intern's heart skip a beat. Tom was in the process of filling out shipping vouchers for Type X controlled items, the highest classification there was, reserved for recovered alien technology or terminators, or so Rolland assumed. Quickly sitting down Rolland was disappointed to see that there were no descriptions, just an unhelpful lot number, but the voucher was 68 of 92 in the approval queue, even tho he knew he could go to prison, a plan was already formulating in Rolland's mind. Quickly selecting the destination box he saw the list of approved Black facilities that could receive a Type X shipment. Rolland's smile grew as he saw that the Applies Technology lab at his University was still on the list, despite having been mothballed 3 months ago due to a budget reallocation. All it took was a single click to make a change nobody would notice.
Four weeks later a doughy student in an IT department T-shirt walked down a back hallway in the Gates Applied Physics Center a computer cart in tow. The unmarked high security door has been locked only with the building master key, the security system disabled. Unlocking the door Rolland slipped on a hooded T-shirt and a pair of sunglasses before slipping inside. Had anyone been monitoring the surveillance video all they would have seen was a shadowy figure walking up to a single wooden crate, loading it onto a cart then vanishing out of frame.
Chapter 2
Freya Windscale (Sierra) motionless body began to stir as her mind returned to its fully active state after a good 6 hours of downtime. To a casual, or even intimate observer Freya looked completely human, from her warm supple skin, to her fiery red hair and athletic build, but the woman on the bed was not human, in fact she wasn't even organic, she was a Sister, an advanced human form android created on an alternate version of Earth, but she was more similar to her flesh and blood She had had another of those dreams again, and the slight wetness at her crotch was a physical indication of its impact. Unfortunately on playback it was just a jumble of semi-realistic sensations and imagery lacking most of the impact from when she had been in an altered state, still it managed to get her more than a little aroused. However on this morning she has no time for recreational activities, she had a weapons re-qualification test scheduled for 0900 hours and she had been up late last night with her friends in the Link. Her bedtime was cutting it close for her to have still gotten a full refresh cycle and now she had to rush to get down to the range.
( Reference Pic for Freya )
Sliding out of bed Freya reached for her blue metallic bodysuit, which served as a basic undergarment and, when activated, a critical piece of protective body armour. Most Sisters never took it off, paranoid about being caught in a vulnerable position where they could be disabled or worse, reprogrammed, but Freya just loved the feel of the bedsheets on her naked skin. The suit had the cut of a long sleeved leotard and protected the vital components of her processor bay and power core in her chest while allowing for maximum range of motion and ease of repair for her legs and head. Once she had it on and adjusted all it took was a quick mental command to activate the suit, bonding it to her skin and energizing the active shield elements within. Looking in the mirror she admired her perfect figure, her suit hugging her body without a wrinkle to be seen as it had literally become her skin. Checking her chronometer Freya grabbed her duffel bag and ran out the door to her flat.
The bright sunlight was filtering down through the old trees that lined the building's courtyard and surrounding street. A few vehicles whirred about on the streets, but the base had been designed to be easily traversed by the tireless female androids and it took Freya only 5 minutes to cover the 2 miles to the firing range. Freya was due to be assigned to a new rotation and needed to post updated scores in order to be properly evaluated. The range consisted of a series of high walls around a several acre simulated urban and suburban environment with the latest in holographic special effects. Waving her hand in front of the access pad at the side entrance Freya authenticated herself and received information about which of her squad had already checked in. She soon found them donning their gear in the ready room, all dressed in similarly colored leoarmour covered by combat utilities.
"Hey, sorry about being 4 minutes late, I had a, late night last night, you know what I mean," Freya smiled, trying to cover over her oversight with humor.
"Don't sweat it," replied Bryce, she was taller and slightly butch looking. As expected she was the designated heavy weapons Sister of the unit. "They put in another group in front of us so we'll be sitting here a while."
"I heard you've put in for a transfer," said Eyn, looking up from her field stripped sniper rifle, "shame to break up our group, we're rated one of the top 10 in this sector."
Freya sighed, "I know we've made a great team, but I just need to try something in covert field ops, solo work."
"What are you crazy Freya?" said Bryce, putting down her minigun. "You're at the top of your game, your mental agility will never be this high again, why waste it spending it sneaking around some creator forsaken rock filled with smelly biologics. Covert ops is for retirees on the downslope."
"Shut up Bryce," snapped Eyn, "there are others around, that's hurtful and unnecessary."
"We've had this argument before girls, its only temporary duty, I'll be back in three years, you'll have a chance to cross train my stand-in. Our unit's been together for 20 years now, I need other experiences besides special forces combat to properly expand my codebase."
At that time the squad all received a message informing they were next up on the range.
"Alright Sisters, its our time in the hotseat," said Freya, standing and shouldering a grenade launcher, "I'm expecting a new course record as my going away present." Freya held out her left arm as it morphed into a silver plasma bolt launcher.
Bryce, Eyn and the rest of the squad smiled back and saluted their leader. "Yes sir," came the response in unison.
The squad entered the range and immediately spread out into a standard tactical formation. Freya had a real time position plot in her visual sensorium of all of the squad members, superimposed on the map data that was available for this scenario. Mission orders then flashed into Freya's mind, tactical assassination with hostage rescue as a secondary objective. Target was a Virtualizer mistress with likely opponents consisting of Metal Drones. Freya passed the information on and quickly sent out waypoints for her fire teams to follow. Quickly and silently her team of Sisters began to move through the simulated environment.
Freya had the honor of drawing first blood when around a corner she encountered a statuesque silver metallic male drone. It's arm was barely able to raise 30 degrees before Freya but a plasma bolt through its head. The other members of the squad were instantly informed that the element of surprise has been lost and in unison began to take out the targets they had been tracking. Separating from Bryce, Freya took Eyn on a run trying to close the distance to the headquarters before more drones could be summoned. Their luck ran out in the middle of a wide plaza where a number of drones soon had them pinned down.
"Hey Lieutenant, are we going to make a move or just work on our long range target practice all day," quipped Eyn, picking off another drone with her railgun sniper rifle.
"Don't worry, B Team has the rear road covered, our target isn't going anywhere."
"It's not our target I'm worried about."
"Oh ye of little faith, come on, we need to draw more of their fire."
Eym complied, but then yelped when a blast of MILES plasma hit her arm. "you know we get points off for getting hit and a LOT of points off for getting killed."
"Yeah, I guess we have enough of them...", with that Freya raised her hand slightly and signaled towards the mass of drones confronting them. Second later the air was filled with the buzz saw roar of a minigun as every last drone was blasted apart by Byrce shooting down from a window overlooking the plaza.
Eyn blinked. "You mean us sitting here was a trap?"
"That's why I'm in command, now get yourself to someplace high and cover my sexy ass, I'm going in."
Freya ran across the plaza to an alley and proceeded to chimney leap up 6 stories to the roof level. Looking up she could plainly see the headquarters building, surrounded by an energized plasma fence and two rings of concrete pillboxes. Within 5 seconds of receiving the mission orders Freya had pattern matched the scenario with the highest projected score, it also carried a significant probability of failure as most of the plan hinged on what she was about to do next. Morphing her arm back to its regular appearance Freya proceeded to draw both her railgun pistols and then using a runner's crouch accelerated herself down the roof with inhuman speed. The drones weren't pushovers and about 3/4th the way to the end she began to take fire, random at first, but quickly becoming concentrated and deadly accurate. However Freya, her mind, body and perception, was faster than a bunch of holographic drone simulations, she ducked and weaved, leapt and tumbled before taking a final two steps and launching herself into the air, far above the plasma fence and entrenchments. She landed on the opposite roof with pinpoint accuracy, rolling to burn momentum and at the same time shooting two Drone guards through the head with her pistols. She continued her tuck and roll down a conveniently placed stairway bowling over a pair of drones rushing to the roof and quickly dispatching them.
Struggling to her feet Freya gasped for air in order to cool her overheating internals. Her AI processors had the ability to automatically overclock and focus resources in response to threats, in much the same way that a biological human's brain triggered the release of adrenaline and other neurotransmitters to increase short term performance. What Freya had just pulled off was extreme, even by her standards and now she was struggling to get her systems out of the red zone. Hearing the footfalls of approaching drones Freya pulled out an anti-matter grenade and rolled it down the stairwell. Turning back around to face the door as the shock wave rushed around her Freya calculated that she had about 5 minutes to defeat a literal manifestation of a video game Boss. Pistols drawn Freya kicked in the door and came face to face with the range's best simulation of a Virtualizer. It was a woman, a very hot woman, tall, thin and with ever inch of her body below the neck covered with a latex textured silver suit. Freya immediately emptied both of her pistols into the woman, forcing her back against the wall, but the woman just glared as the holes in her suit were stitched together with black tendrils before silvering over as if nothing had ever happened. The bot woman's arm morphed into a nasty looking cannon and began to blast away at the inferior technology droid that had dared enter her command room.
Freya was able to dodge about five of the blasts before her red lined processors began to cry out for relief degrading her performance and resulting in the sixth blast hitting her square in the chest. Despite being a training device Freya was still blown back through a desk and into a wall. Rolling behind a pile of boxes for some quick cover Freya morphed her arm back into the plasma bolt launcher and responded to the femboss with a barrage of armour piercing plasma. Again Frya soon exhausted her ammunition supply allowing the bot's silver body to magically heal.
The Virtualizer smirked with contempt and slowly raised her arm-turned-cannon. "Is that really the best you've got you primitive little fuckbot?"
Frya stood up straight and looked the evil simulated bot in the eye. "Yeah, that's the best I've got, but I can't speak for the rest of my team."
The Virtualizer turned her head toward to open window - just in time to watch the anti-tank missile impact her body, ripping it to pieces and sending her head rolling about the floor, as it yelled out with an electronically distorted scream. Freya calmly reached into her vest pocket and pulled out a small injector filled with a silver nanno-goo and jammed it into the open neck stump on the screaming head. A few seconds later the head turned gray and crumbled into dust.
//This is Squad leader, primary target eliminated. Beta team report status of secondary objective. Thank you Bryce, nice shooting.
//No problem Lieutenant, you need any more cover?
//Yes, I will be self-extracting to the rear, engage any residual forces and rendezvous at Point Charlie
//This is Beta squad, all organic prisoners recovered, extracting to Point Charlie.
Freya took a few deep breaths and watched in her HUD as her squad began to redeploy for the extraction operation. There were still plenty of drones around, but she could allow herself a few moments to get her systems back down into at least the yellow. It has been a tough fight and she had taken a lot of risks going off on her own like that, but she knew that her NCO's could be trusted to carry out her tactical plan with little correction. With the score she hoped to achieve there was no way the Commander could refuse her transfer request now.
Chapter 3
The squad members each lifted a small shot glass full of a glowing green liquid high, then quickly sent another round down their throats with reckless abandon. The bottle of radium-spiced Glow was their prize for setting a new course record and the capstone on Freya's tenure leading her Special Services squad. Not only had Freya had scored a personal best, her mental processing levels were a full 2% higher than her last assessment a quarter cycle ago. She was at the peak of her abilities, she could probably get any tactical combat placement she wanted, even in the Federation's fleet as an exchange marine, but instead she wanted something off the typical career path. Later that day she would learn if her wish had come true.
As the squad celebrated in the ready room the became aware of soft sobbing from an adjacent room,a few instant messages later Eyn had the story.
"It's Major Hashi, she....she's dropped below the red line."
The room went silent, the Major had been the Group commander since well before everyone in the squad had been initialized.
"How old is she?" asked Bryce.
"371 cycles."
There was a murmur of respect, the Major had managed to hang on to her tactical position for far longer than was typical for a Sister.
"Her mind must be of superb quality," remarked Freya out loud.
"Yeah, but runtime catches up with all of us," said Eyn.
Everyone in the squad felt bad for the Major, her mind now judged to be too "slow" to engage in front line tactical combat operations for Special Services. While most wondered if she would continue on in a support role, where her experience and creativity could prove an asset, or retire to some place unknown to live out her final cycles before she reached the limit, Freya actually felt happy for her. Soon the major would be able to choose in one way or another to transcend her synthetic existence, her AI code and core directives and become a Natural, either in death or transition. Freya was unable to dwell on this more as she got a message requesting her tele-presence in a conference with the personnel department. Excusing herself from her squad she walked into a private alcove and placed her hand over a secure hard line interface terminal to establish the link into the meeting. The bare walls of the alcove were replaced by the whiteness of a blank VR environment, Commander Illen Savannah was standing there waiting for her.
"Hello Freya, I hope you don't mind if I make this short, I have a lot of transfer actions to go through today."
"Yes Sir, I understand sir."
"I just got your scores, most impressive as always Lieutenant."
"Thank you sir."
"The first bit of good news was that your promotion just came through, Captain."
Freya was a bit shocked at this as she hadn't been expecting another promotion before her 100th cycle.
"Thank you sir, I don't know what to say."
"Don't be so modest, we would have promoted you sooner, but you know how it is with so many high achieving androids living for so many cycles. This isn't Star Trek, we can't make everyone an officer."
Fyra smiled, "Maybe I should go obtain a commission in one of the biologic militaries."
"We're actually recommending that you know, helps promote cross cultural exchange and all that, but the Defence Forces want to keep you all to themselves. This of course brings us to your transfer request....and it was a most unusual one at that. You really wanted to be given a Level 1 covert service assignment?"
"Yes sir, I feel it is the best way to expand my knowledge base at this point."
"Well, it shows your commitment to becoming a well rounded officer that you would want such an assignment at the peak of your abilities. As much as the Covert Service would love an officer of your caliber, I am afraid that even they couldn't justify wasting your abilities like that. Therefore, you have been assigned to be a Field Chief of a level 2 covert operation."
"L-level 2?" the possibility of being denied her dream position was taxing Freya's finely tuned personality matrix, causing her to stammer. "B-but why? Am I not the most qualified candidate?"
"You are Freya, by far, but that's the problem, you know the Level 1 assignments are reserved for those approaching the limit. It's not just a matter of preserving your own runtime, but those Sisters, they need a place where they can remain useful. I hope you understand."
Freya did understand and she couldn't argue with the Commander. It was selfish of her to try to pursue something that would be a luxury to her when some of her Sisters, like Major Hashi were being devastated by the approaching limit. Freya came to attention and saluted the Commander. "Thank you for the new assignment, I will do my utmost to succeed in the mission."
"I know you won't let me down, you're like a daughter to me."
With that the virtual conference closed.
Freya took a deep breath into her heat exchanger as her processor was still working overtime. She tried to consider all of the ramifications of her transfer and potential courses of action available. After calming down and organizing her thoughts, she realized the only thing she could do was take the post, do her best and then just throw her secret desire over the fence until she was in a position to actualize it. Walking back out to the ready room Freya excused herself from the squad party, gathered her things and began to jog back to her residence. Even though it was the middle of the day Freya desperately wanted to get back into the Link to decompress. There was nowhere she had to be so it was doubtful anyone would notice or care if she took some unauthorized personal time. Freya kept running all the way to her doorstep and once inside she tossed her bag on the bed, sat down in the chair and plugged the Link cable into the back of her neck without even bothering to remove her combat gear. The hyper-modern interior of her living space faded away into a tree lined suburban street in a generic mid-21st century human world.
The Virtual Link could be thought of the near ultimate evolution of the more primitive escapist worlds like The Sims and Second Life employed by biologic species for centuries. As androids the Sisters had effectively no overhead in accessing or experiencing the full features of the Link, but bandwidth and processing constraints rendered the Link an imperfect simulation of the real world. Even if 75% of biologics couldn't tell the difference most Sisters could, but like most simulated worlds those that came to enjoy them weren't looking for a flawless experience. Unfortunately for Freya her needs were outside the parameters defined by most of her Sisters. Walking into the back yard of one of the houses Freya saw her best friend Val tanning herself in the midday sun.
"Hey Val, you stay here all night or did you leave and come back."
Val lazily looked up, "Woah, what are you doing back so early. You didn't get fired or something, did you?"
"Actually I got promoted."
"Oh wow, I'm so happy for you. Hey, guess what, I got promoted too!"
"That doesn't count, Val. You're self employed!"
"Self employed is still employed!," Val pouted.
"Yeah, you look real busy. Listen, I'm sort of needing some help to take my mind off of things."
"Well, you know I'm usually free, what's wrong?"
"I got my transfer orders today..."
"And???"
"I am going to be the Field Chief of a Type 2 Covert Action," Freya said with a sigh.
"Type 2....but you are the top rated officer in the Sector, how could they not give you your first choice?!"
"Guess....Type 1 jobs are reserved for those approaching the Limit. It...it makes sense. They need the jobs more than I do and Command doesn't want to squander my abilities."
"I'm so sorry Freya. I guess there's just no way to have your cake and eat it too."
"Yeah, I'm just being impatient, I'll have centuries to indulge my fetish and until then we always have the Link and the Humans that frequent the star port.
"Oh!" said Val perking up, "You didn't tell me how that worked out last night."
"Terrible, just like my day. I wasn't wearing my armour and this really rip guy comes over, I think he was an officer, anyway he comes over and we start to talk and I am really getting a good vibe..."
"And??"
"Well we're just about to retire to a more private setting when the waitress comes over with the Glowing Gin I had ordered. I pick it up and I see the guy's just staring at me. I ask what's wrong and he makes some lame excuse saying he's not into bot play."
"What?"
"Yeah, that was my reaction, but I tried to play it off and tell him half jokingly that just because I'm a Sister it doesn't that I am going to hook myself up to some remote and strut around the hotel room with my abdominal panel open."
"Well what did he say to that."
""Sorry, but I am really looking to have kids and I don't get involved with women unless there's a possibility it could go somewhere.""
"Ouch, that was mean."
"It's not fair that Humans have such wonderful bodies, but such bigoted small minds."
"Hey, don't go stereotyping them yourself. Maybe I can help take your mind off of things," said Val, moving to comfort her friend. Did you hear that the new 3.4 version of OpenHuEmu came out today."
"Really?" said Freya her expression brightening. "Have you tried it?"
"Running it right now."
"Well, is it better?"
"Kinda better, I'm sending you the download link. Oh, they say it has improved intoxication support, but they only guarantee it up to a level of .005."
"Really, well that's not much, but better than nothing."
"Yeah, I still find it kinda jittery, did you get the package installed yet?"
"Just about, hold on, let me update my perception filters."
Freya closed her eyes and loaded the software module that would make her Virtual feel and act like it was made of flesh and blood instead of hyper-alloy and polymers. The HUD and GUI disappeared from around the periphery of her vision, which itself became softer and much less detailed. Her other senses followed a similar downgrade path just before Freya felt a heart begin to beat in her chest, lungs expanding and contracting, a digestive system pushing food through to be absorbed. Her pussy changed from a polymer pouch and fluid tubes to a fleshy organ, already dripping with human smelling juices. Her mind, calculating and exact, seemed to fuzz over, sensations becoming indistinct and vague, but, to Freya at least, much more sensual and erotic.
"Mmmm, I told you it was better, look how fast it got you going." Val reached up and pulled her horny friend down on top of her, her hand reaching down to Freya's crotch, a playful finger pushing inside her organic slit.
"Ooooo yeah, that feels great. Get me all hot and sweaty Val, make me stink like a human!"
The two simulated humans began to make out on the grass next to the virtual pool, their hands rubbing each other's breasts, fingering each other's pussies.
"Ooooo, Freya, damn your skilled with your fingers! You know, after this, I think I might have to go to use the toilet."
"Ahhh, that's sooo hot..."
Val and Freya continued for about an hour enjoying multiple organic orgasms and various esoteric pleasures of the human body. By the end of the session both Sisters were left gasping for air, as their simulated bodies were just aching with fatigue.
"Whew, I love how we get tired, it really motivates me to get the most out of the time because I can't just go on forever," remarked Freya.
"I know, and it really changes the experience dynamically instead of getting the same cookie cutter intensity each time. Best part is that because we're played out we have to find some other erotic activities to do....mmm, like skinny dipping."
"Or making a nice dinner, while naked."
"Hey Val, you never told me if you got into the whole ASFH scene before or after your Exchange period."
"Oh, I was like you, I only got into the whole Human fetish after that year I spent in organic form. I mean I was only 20 cycles old, and only 5 in the physical world, I wasn't old enough to know what the hell I was into."
"That's the irony Val, the hottest, sexiest period of my life and I didn't know going in to take full advantage of it."
"It's even more ironic that our time spent human is the one part of our life we weren't able to just record and then playback later. All my memories of all the sex I had are so vague, I can't even recall what half the guys looked like!"
"Did you ever stop to think that the only reason we're into Humes is because we can't fully remember what actually happened and our AI's filled in the gaps with sort of an idealized version?"'
"Sometimes, but then I talk with some of the others on the forums that have actually transformed again and they all say it was just as hot if not hotter the second time around. I the beauty of biologic life, there's so much noise in the system no two experiences are the same or can even be adequately be simulated or predicted."
Val's comment forced Freya to confront the reality that no matter how large the open source community became for the Human emulation software, it was never going to be the same as actually being a biologic Human. At her core, Freya's Personality Matrix was still composed of AI code. Her processors crunched discrete digital data, not vague neural impulses. Her sessions in the Link were relaxing, but they just couldn't compete with actually being flesh. Freya knew the bind she was in, she was at the peak of her mental capacity as a Sister, she had enough experiences to get rid of the stiff robot like personality of a newly initialized Sister, yet didn't have centuries worth of them gumming up her personality matrix and slowing her thought processes. Spending time as a human greatly increased the complexity of her Personality Matrix if and when she would change back to her Sister form. Too much time as flesh could blow Freya right out of her most productive cycles, this is why Command refused to assign her to a post that involved a conversion to an organic human form, they would have been throwing away one of their most valuable assets.
Freya turned back to Val and proceeded to cuddle her fellow Sister for a few more minutes before finally standing up and stretching out her faux Human body.
"So, what's for dinner?"
:p ) I'm actually hoping that people will take an interest in the story and bring up questions I haven't fully addressed. 
It's basically the uncanny valley in reverse, many Sisters would see a human as a creepy imperfect version of themselves, which is kind of a turn off. Like Dyson bots Sisters generally take a lot of pride in their synthetic nature and bodies (although there are deeper reasons behind this) and as they are fully bisexual they usually find their own shells quite arousing. 