Disclaimer: I don't own Supergirl.

Author's Note: I've always had mixed feelings about Soulmate AUs and the stories spawned by them - I usually love the idea, but in practice I never see it written (in longer form anyway) in ways that fit my highly idiosyncratic tastes. And of course, not being able to find fics that fit my idiosyncratic tastes for a ship, character, fandom, trope, etc, is usually where I get my fanfics from, at least in part. Usually I have to combine that idiosyncratic need with some other notion or idea and go from there. And thus, we have this story.

If you are someone who utterly and completely hates Mon-el, this is probably not the story for you. While this story is and will completely be Supercorp, without anything that could be really interpreted as Karamel, I quite like the character in of himself and think he was and interesting and fun character and he brought something useful to the table, narratively speaking, for season 2. For the record, on the Mon-el and any other front: I have yet to watch Season 3.

There will be, once we get to him, nearly as many scenes from Mon-el's POV as from Lena's, because I am weaving two story threads together into this one story - a Supercorp Soulmate AU and a 'Kylia Tries Her Hand At Writing Mon-El To Her Idiosyncratic Tastes' Season 2 Rewrite. We'll see if it works as well in practice as it does in my head. It might not.

This fic will be a Season 2 rewrite, starting from Episode 2x03, diverging outwards - slowly at first, but more and more as the story goes forward. I tend to assume an episode starts on the date that it airs, unless it is a two-parter, explicitly follows on a short time from the previous episode or some specific amount of time between episodes is established

As a final note, this fic is un-beta'd, and on the off-chance anyone reading this is interested in helping me out on that front, my tumblr is Kyliafanfiction, where I also also make posts about my fics, fandom and fanfic culture in general and the various fandoms I'm in.

One In A Thousand

By Kylia

Chapter 1: Unanticipated

Lena Luthor had never really thought she'd have a soulmate.

Not just because of the lifetime of rejection her adoptive mother had given her. Not even because of the baggage of her last name - after all, who would want a Luthor, the sister of the man who had gone insane and nearly destroyed Metropolis, among other sins, as their soulmate?

No, the primary reason Lena never expected to have a soulmate was simple mathematics. Only about one in a thousand humans (some estimates put that down a bit further, to one in two or three thousand) had a soulmate. The vast majority of humans, unfortunately, had to handle questions of love, relationships and marriage with merely human faculties, muddling through romance and dating the mundane way.

Of course, until you actually made physical contact with your soulmate, you never knew that you had a soulmate, which had always struck Lena as such an incredibly inefficient system, to put it mildly. People could be married, even have children, when they finally met their soulmates. But almost every culture in history, it seemed, even the ones with the strictest laws about divorce or annulment, seemed to make exceptions for soulmates - often interpreted as the will of God or the Gods - and by all accounts, things usually worked out for the best for everyone involved in such situations, even the spouse left behind. Usually.

Like most children, Lena had, when she was younger, wished for a soulmate, dreamed of meeting her perfect match. She'd only ever entertained such thoughts for a fairly brief time in her life, however. The odds were simply not in her favor - on a planet of over seven billion, one tenth of one percent did mean some seven million people did have soulmates, which only seemed large when it wasn't set against the raw number of people there were. 0.1% just wasn't that great of a chance.

As things stood, Lena was quite sure she had used up the lion's share of her lifetime allotment of luck when she was adopted by a family as well-off as the Luthors following her birth mother's death. Even if, especially in the last few years, it didn't always feel like she'd been all that lucky.

All that said, Lena remained fascinated by the notion of soulmates. A part of humanity since the beginning, as far as anyone could tell, the 'soulmate phenomenon' had been discussed by countless thousands philosophers, theologians and scientists, all trying to make sense of it, to fit it into their way of looking at the world, to understand it. Authors, artists, poets and musicians had contributed to the discussion in their own way, portraying soulmates and their stories in every conceivable way.

Modern science had come to a few broad consensuses about soulmates, but only in the most general terms. There seemed to be a genetic component, in regards to whether or not someone had a soulmate, but it didn't seem to be entirely genetic. Attempts had been made, with only middling success at best, to predict if people had soulmates, or even what kinds of person someone might have as their soulmate. But still, researchers in the field had thought they were making progress.

Until three years ago, when the first confirmed case of someone having an alien as their soulmate had been found. No aliens, as far as anyone knew, had soulmates, at least not in the way humans did. But the notion that a human could have an alien as their soulmate? An alien not even born on this planet? That had blown up countless theories and assumptions, especially when, in the years since, several more cases had been found and confirmed, and several dozen more supposedly extant, but as of yet unconfirmed. There was even a book written by one of the confirmed cases. Lena had bought it when it came out six months ago, curious... but she'd never gotten around to reading it yet.

She found herself very much wishing she had when a reporter from CatCo Magazine came to her office for an interview.

Lena's Office, L-Corp Headquarters

October 25th, 2016

When she'd gotten the request for an interview from Kara Danvers, Lena had been happy to accept. Her guess that the other woman had been a reporter hadn't been correct at the time, but she had picked up on something that had made it clear that's what she aspired to be. And she was right. Again.

Lena was used to being right about things.

She'd accepted for several reasons. First and foremost, because Kara Danvers had seemed quite open to believing that she wasn't her brother, that she was genuine in her desire to have the Luthor name stand for something positive again, to have L-Corp be a company people trusted once more. She'd certainly been far less suspicious and hostile than Clark Kent, though he had at least somewhat come around before returning to Metropolis.

Given who he was, that didn't surprise her. Clark and Lex had been friends, until her brother had become too vocally anti-alien for the reporter to accept it. He'd been burned by a Luthor before - compared to some people, he'd been shockingly fair minded when she'd professed her innocence.

Which was even more surprising given who Clark Kent really was. When she'd found those - well hidden - files her brother had left behind, in the company's systems upon taking over Luthor Corp, she was stunned she'd never put the pieces together before. That no one else had. Once you knew Clark Kent and Superman were the same person, everything made a great deal more sense.

Then again, Lex only figured it out because he managed to capture a clear image of Superman's face and ran it through the best facial recognition software known to man - best because he invented it that way.

When she'd realized that her brother had known Superman's real identity for years and done nothing with it... well, she'd been confused. Until she'd finally mustered the courage to read his journals. She hadn't been able to get through them all, especially the last ones that had been increasingly manic, frantic with their hate and bile, his obsession with defeating Superman, with saving Earth from the alien menace. They'd never quite reached incoherence, but they got close.

But she had read many of them, parts of others, and been able to draw some conclusions.

As best as she could guess, at the end of the day, for Lex, it had been as much about beating Superman as protecting Earth from the alien menace. Proving that the ingenuity of man - his ingenuity - was enough to stop even the Man of Steel. It wouldn't have been a fair fight to go after Clark Kent or his family, friends and loved ones like that. So he didn't.

Lena also liked to believe - or hope, at least - that some lingering affection for his onetime friend had stayed his hand on that front. At least a little. She had no proof, no real reason to believe it, but she wanted to nonetheless, to believe that there was some semblance of the older brother who had been a good man was still there, underneath all the hate and jealousy and rage and bigotry. Underneath all the insanity.

Which brought everything back to Kara Danvers - why was someone who wasn't a reporter yet, tagging along with a reporter from a rival paper that just so happened to be Superman? Who had the right hair color and really, how was anyone (herself included) even partially fooled by those glasses? There was an obvious potential answer, of course.

It was hardly proof, but combined with Kara's genuineness, how nice she'd been, how much she'd clearly wanted to help Lena, and how much she seemed willing to believe the truth that Lena was different from her brother...

Well, it was a simple choice to give her the interview.

And didn't hurt that, one a purely shallow level, Kara Danvers was nice to look at. Very nice.

"Ms. Luthor," Kara Danvers said as she entered the office, approaching her desk.

"Lena, please," :Lena stood up, extending her hand and shaking the other woman's in greeting. "It's good to see you again Ms. Danvers," The words rolled off her tongue smoothly - they were true, but also pro forma, something she'd said, with many different names, many thousands of times.

But there was nothing normal or routine about what happened when her hand touched Kara Danvers'.

The jolt of pure electricity that ran up her arm and into her body set her blood pumping and her heart beating fast, as if she had just been sprinting. Her breath caught, her vision went blurry save for Kara for a split second, and then...

She heard and felt it. A name, in her head, as if shouted. Kara Zor-El. And a sharp, stinging pain on her left shoulder, followed by what she could only describe as a painful tingling, spider-web sensation.

"Ah!" Lena's free hand grabbed at her shoulder, as if that would do anything about the already fading stab of pain or the tingling sensation

Lena didn't let go of Kara's hand - she couldn't - but she nearly staggered back under the weight of what had just happened, as it dawned on her. The obvious. She had every symptom, as described countless times.

Kara Danvers - Kara Zor-El - was her soulmate.

Kara was looking back at her with confusion, no recognition on her face, no sign that she'd experienced anything like what Lena just had.

Which shouldn't have been possible... except...

Well, between the name shouted in her head and Kara's lack of reaction, Lena had no doubts about her theory as to why Kara had been hanging around with Clark Kent.

"Lena - are you alright!? What's wrong?"

"I'm - I'm fine." She looked past Kara to Victor Pine, one of her personal security detail, who was standing by the door. If he had any realization as to why had just happened, she couldn't tell from his expression. "Victor, could you give us a moment? And close the door on your way out?" The man nodded after a moment and stepped out of her office, closing the door behind him.

"Lena-" Kara blinked in confusion. "What's - what happened? Are you hurt?"

"No, I'm not hurt," Lena said, her mind racing as fast as it often did, trying to figure out the best way to do this. Supergirl - Kara Danvers... Kara Zor-El - had been on Earth for some time, so she had to be aware of the soulmate phenomenon among humans. But as an alien, she wouldn't likely imagine she could have a soulmate.

But Kara didn't know. So Lena could control just when and how she told Kara. It didn't have to be right this second, as happened with humans who met their soulmates - both knew at the same time. It would give her a measure of control over the whole process, which Lena found appealing.

I shouldn't tell her - she's a Super... she might have believed me before, but I'm still a Luthor. I can't tell her yet.

And yet... Lena hated that idea. She didn't want to lie to her soulmate - not a great way to start things off, to say the least, and given that she'd long since assumed she'd never have one...

Lena wanted it all, and she wanted it to be perfect, or as perfect as it could be.

And she didn't want to wait. Not any longer than she had to. It was all so surreal, and any second now, Lena was worried she'd wake, or somehow... it would all go away.

Lena let go of Kara's hand and pulled up the sleeve of her shirt slightly, revealing the writing on her left shoulder. Writing that was in no lettering or language she recognized - not one from Earth. She glanced over at Kara, whose eyes had widened for a split second upon seeing the words that had to be Kryptonian. She assumed.

"I don't read Kryptonian - that's what this is, isn't it? - but I'm going to guess this says Kara Zor-El? I can't imagine it says 'Supergirl', for obvious reasons."

Kara flinched a little at the name, at her name, at the connection between Kara Danvers and National City's resident superhero... She bit her lip, looking down at the ground for a moment. Lena wished she knew exactly what was going through the other woman's head right now.

But Lena wasn't even sure what was going through hers. She felt... almost giddy, which a clinical part of her noted was an extraordinarily common side-effect of finding one's soulmate. She couldn't believe what was happening, that she had a soulmate, that she had a perfect match...

That her perfect match was an alien - that she was a Super. A Super and a Luthor as soulmates sounded both so cliche and obvious and... so very impossible.

Which also left her nerves tightening into a solid ball in her gut, as the prospect of this not being possible. Almost every single time soulmates found each other, they had a happy life together, as long as they both lived. Almost.

And Supergirl - Kara - had nearly died more than once... Girl of Steel or not, invulnerable to most forms of injury or not, she could still die. Die tomorrow. Die next week, die

Her birth mother had died. Her adoptive father had died. Her brother was insane and in prison for seventeen consecutive life terms. Her adoptive mother had never wanted her to begin with.

That little dark core of fear asked her the obvious question - couldn't your soulmate leave you too? One way or the other?

Lena closed her eyes for a moment and inhaled sharply, forcing her thoughts into something resembling rational coherence. She'd have to deal with all this more, when the reality of what was happening really hit her later, but she needed to focus on the now.

"This-" Kara started, stammering a little, "this- how can - I mean, how can I be your soulmate? How is that even - I'm an - I'm not human!" At least she isn't trying to pretend she isn't Supergirl. Probably too stunned by it all to even try. "How is that even - it's a human thing, soulmates! Kryptonians - we don't - and I mean, there's - I don't even... what the heck?"

"Actually, there are a few confirmed cases of humans having alien soulmates," Lena said softly. "Soulmates have always been a topic of academic curiosity for me," she added by way of explanation. "It's thrown soulmate researchers into fits of confusion, but it is possible. Quite evidently." Lena paused a moment, before going on before she could stop herself: "Soulmate tattoos are impossible to fake, when examined close enough. If you'd like, we could have-"

Kara interrupted, shaking her head, "No... no you don't need to - I... I believe you. I just... I never expected - for obvious reasons..." She closed her eyes and took a breath. "And I'm not used to being... well, outed as Supergirl. By a tattoo, of all things."

"I actually suspected you were Supergirl already... this just confirmed it." Kara blinked, looking at her in confusion, and looking almost... disappointed. "I'd like to say that it was just because glasses don't actually make for a good disguise, but it was more that the fact you first came into my office with Superman that was suspicious."

Kara started to try to protect her cousin's identity, but Lena shook her head.

"My brother... he's many things, most of them bad, but one of them is clever. He did figure it out. I found the files he had proving that Clark Kent and Superman were in fact the same person." Kara's eyes widened, and Lena shook her head. "They've been deleted, and I set a program to dig through the rest of the company's networks to erase anything else he may have left behind with that proof."

Kara let out a breath. "That... thank you." Then she suddenly giggled, "He'll be sooooo annoyed when I tell him his arch-nemesis knew who he was!" She took another deep breath, getting control of herself. "Sorry. This just feels..."

"Surreal?" Lena suggested, and Kara nodded. "Maybe we should sit." She took her own advice and sat down, Kara following suit. "I'm not entirely sure how to process this... the part about this that makes the most sense is that my soulmate is a woman."

Kara nodded, letting out a small chuckle. "That part would be pretty mundane compared to... well, everything else. So... you already knew you were... gay?"

"Bisexual, actually, but I tend to prefer women." Lena explained with a smile. She looked Kara over again quickly, seeing, that she knew to look, the hints of Kara's musculature, and wondered - she allowed herself a moment of it - just how those muscles would feel under her hands...

She really is quite lovely. To put it mildly.

"And... the fact that I'm a woman doesn't surprise you?" Lena asked, wondering. It didn't seem to, but Lena wanted to be sure.

"I suppose by Earth terms I'm bisexual - on - on Krypton there just aren't specific words for... sexual orientation. It's just attraction who whoever you're attracted to... romantic interest in whoever - whoever you're interested in -" Kara as speaking quickly, almost babbling in a way that managed to be endearing and adorable rather than annoying. "I mean - I've - I've never been in a serious relationship with a woman, and I've usually only ever gone after guys I was interested in but - I mean... no, it doesn't surprise me, not compared to actually having a soulmate and... I mean, you're a really really pretty woman and kind of took my breath away when I first saw you when I came in with Clark and I'm going to stop now before I dig the hole any deeper," Kara took a deep breath, her cheeks pink.

"Breathtaking, am I?" Lena raised an eyebrow. Kara just nodded, keeping her mouth shut for the moment. Smiling a little, Lena leaned across the desk a little. "You're rather beautiful yourself, Kara." It was true. Then she settled back into her chair.

"So at least there's an attraction. Unsurprising, but that still leaves the fact that we barely know each other." Lena pointed out, settling into finding a practical solution.

Kara nodded. "And... this -" she swallowed lightly. "I did come here for an interview and if I don't it in before noon my boss will probably fire me and I really want to keep my job," she explained. "I... and I need some time to process this and -" Kara closed her mouth, clearing her throat. "It's just... it's a lot to think about, and... I do need to get a quote from -"

"The sister of the world's most notorious alien hater on the eve of the President signing her Alien Amnesty Act?" Lena finished.

"Yeah." Kara nodded. She frowned, "Sorry."

Lena shook her head. "I'm a Luthor. I can't pretend that I'm not just because it's inconvenient." She considered for a moment. "Why don't we have lunch, tomorrow?" A lunch date was far lighter than a dinner date. It would let them get to know each other, figure out how all this world work, in a controlled, low-pressure context.

"Like a date?" Kara blurted out, then her cheeks flushed again.

"That is the idea, yes. A date." Lena smiled again. Kara looked adorable when blushing. "Something light, no strings attached. Just getting to know each other? We can do the interview now and... then we'll both have time to process this revelation. It's probably going to take a few hours for it to really hit me that Supergirl is my soulmate."

Kara smiled broadly, and Lena decided she wanted to see that smile on a regular basis. Slow down girl!

"A date, then." She nodded, still smiling. "Unless you had somewhere in mind - I know this great place, just a few blocks away from here. It's a bit out of the way, and usually not super busy, so it'd be pretty private and they make some of the best potstickers in the city."

"That sounds good," Lena agreed. She held out a hand. "Let me program my number into your phone."