Sin x Secret
Supergirl. Baby Danvers x Lena Luthor. Kara Danvers. Alex Danvers. Kelly Olsen. Nia Nal.
Word Count: 3.9k
“So that's it?” Lena asks, voice low and uncertain, as if the answer might kill her—even though she’s the one who said it first. “We’re… done?”
“Yeah.” You can’t believe the word comes out of your mouth. How can you and Lena be breaking up when you love her so much? “I—I think so.”
You just sit there, staring at each other from opposite ends of the couch. Silence settles between you, heavy and fragile like glass.
“There’s just one tiny thing,” you say. Lena raises an eyebrow. “Alex’s engagement party tomorrow.”
“Oh, fuck. I forgot about that.”
You both groan at the same time, and it’s almost funny. Almost comforting. Almost like nothing's changed. But it has. Everything has changed.
“Look,” Lena says, folding her hands tightly in her lap. “I don’t want to lie to anyone, but—”
“Tomorrow isn’t about us,” you complete. “We’re not going to ruin their party. We can tell them afterward.”
Lena nods, slow and reluctant. “Right. After.”
For a second, it feels like you’ve agreed to more than just a secret. It feels like you’re promising not to fall apart—at least not where anyone can see.
She stands, smoothing her clothes even though she’s in pajama shorts and one of your old hoodies. “We should figure out how we’re going to play this.”
You force a weak smile. “You mean how to fake being in love with you for an entire evening?”
Lena looks at you. Looks through you. “I don’t think either of us has ever faked that part.”
It’s a punch to the chest, the way she says it. Soft. Honest. Dangerous.
You look away. “Okay. So we’ll do our part. We’ll smile, hold hands, take pictures, laugh at Kara’s dumb speech, slow dance if we have to…”
"Kiss?”
It’s a simple question. An obvious one. But it knocks the air out of your lungs. Because yeah, you’d kiss Lena in a heartbeat. You’d kiss her right now.
But what if you can’t stop? What if her mouth ruins you all over again? What if it feels like home, and you have to walk away from it anyway?
“I don’t know,” you admit, voice hoarse. “Can you?”
Lena doesn’t answer right away. She just stands there in the doorway, hands clenched into the sleeves of your hoodie—hers now, you guess. Her eyes are glassy in the low light. You can’t tell if it’s anger or heartbreak or both.
“I’ll try,” she says finally. Then adds, quietly, “If you can maybe not… um, do that thing.”
You blink. “What thing?”
Lena’s cheeks flush red. She looks anywhere but at you. “You know, the thing with the tongue and—”
“Oh. Right. I won’t do the thing.”
You nod solemnly, like you’re making a vow. Even though you have no idea how not to kiss Lena with everything inside you. That’s the only way you’ve ever known how. Like it’s the last time. Like she’ll vanish if you don’t kiss her hard enough to keep her tethered.
She hugs herself. “Thanks. It’s just… I can’t—”
“I get it,” you cut in gently. “Me too.”
A beat.
Then Lena gives a small, crooked smile. “So we’re fake-dating tomorrow, but without the tongue.”
“Right. Strictly PG-13.” You try to match her tone. Light. Casual. Like your chest isn’t cracking open.
“And the day after the party…” she starts, but her voice wavers, and she lets it trail off.
“We’ll tell them.”
And just like that, the clock starts ticking on the last day you'll ever be hers, even if this time is just pretend.
You're late, which is not surprising to anyone—though they act like it is. You've tried being on time before, you swear, but time is a construct and it used to move completely differently on Krypton, so really, it’s not your fault. Besides, being able to cross the city in under a second has made you... a little lax with punctuality.
“You're late,” is the first thing Lena says when she opens the door to her penthouse.
And it hits you like a slap—not her words, but her. The way she looks. Her hair woven into the prettiest braid, neat and effortless in that way only Lena can manage. The black dress fits her like a whispered promise, hugging every curve you know by memory now—each line of her body a path your hands used to trace in the dark. And then there's the slit in the front, plunging too low, revealing the soft line of her cleavage. Your eyes follow it without thinking, like a reflex. Like your body still hasn’t caught up to the part where you’re not allowed to anymore. She looks like a sin dressed in silk. Like a secret you can't keep.
Your mouth goes dry. “And you look too good. Can you change?”
Lena’s brow lifts. “What? No, I'm not gonna change. We're late!”
“Fine,” you mutter, dragging your eyes away from her cleavage. “But just so you know, you're making this a lot harder than it has to be.”
She laughs, light and unbothered. Like she didn’t cry into your hoodie last night. Like she hasn’t been sitting in your chest like a bruise ever since.
“Let’s just go, Y/N.”
By the time you walk into Alex and Kelly’s apartment, everyone’s already gathered in the cozy living room. Balloons tied to chairs, silver and white streamers trailing from the ceiling. A homemade banner that says She said yes! hangs crooked above the fireplace—Kara’s handiwork, probably.
Alex spots you first and lights up. “Finally! We were starting to think you two got distracted on the way here.”
You laugh too fast. “Traffic.”
“Oh, there’s traffic in the sky now?” Kelly teases, handing you both drinks with a wink. “I’m just impressed you two managed to get your hands off each other long enough to show up.”
You nearly choke. Lena just takes a sip of her wine, cool and unreadable.
You glance at her out of the corner of your eye, searching for something—confirmation, a crack, anything. But she doesn’t flinch. She’s always been better at pretending than you.
And that’s the worst part: this used to be effortless. This used to be real.
Now, every second feels like you're trying to hold on to something that's already slipping through your fingers. And you can't even grieve it. Not here. Not tonight. Not when everyone’s watching and expecting you to smile like nothing’s wrong.
So you smile. And you drink. And you try not to look at Lena too long, or remember what her laugh used to feel like when it was only for you.
But your heart is already screaming.
There’s music and dancing and laughter in the background. You hear it—sort of. It slips through the noise of your own mind, screaming at you to act normal. Just one more hour. Just one more moment. Just get through this.
Then comes the call for a group photo. Someone corrals everyone in front of the banner. Alex is glowing. Kelly is beaming. You try to stand behind Kara, but—
Nia elbows you gently. “Here, switch with me so you’re next to Lena.”
“Oh, it’s fine,” you start to protest, already backing away.
But she’s already moving.
And suddenly Lena is beside you, her perfume subtle but devastating, her hand sliding around your waist with practiced ease—like this is just another Saturday night, like nothing has changed.
You can’t breathe.
“Smile, darling,” Lena murmurs beside you, the word slipping out too easily, too naturally.
And that’s when your brain stops working altogether.
Because it’s not the nickname. Not the hand at your waist. Not even the practiced smile she gives for the camera.
It’s the fact that, for one terrifying second, you almost forget you’re pretending.
You almost lean into her. You almost kiss her temple. You almost believe you didn’t lose her.
And it guts you.
Later, you’re sitting alone on the loveseat, nursing your drink and trying not to look like you’re watching Lena. But, of course, you are. How could you not? She’s across the room, laughing at something M’gann said, her fingers twirling the stem of her wine glass, legs crossed like a goddamn movie star.
Your heart’s in your throat where it has been all night. It’s starting to feel like your ribs weren’t designed to hold it in.
Kara plops down beside you, folding her legs beneath her and balancing a second cupcake in her hand. “Hey,” she says, bumping your shoulder. “You and Lena are acting weird today. Everything alright?”
You freeze.
You don’t mean to look at Lena again, but your eyes betray you. One glance. Just one. And she’s already looking. Smiling softly. Eyes flicking your way like she knows you’re watching her. Like she likes that you are.
Your heart nearly breaks your ribs this time.
“She just…” you start, words catching somewhere in your throat. What are you supposed to say? That you’re broken up? That you’re lying to everyone in this room?
You settle for the only truth you can handle.
“She looks so hot.”
Kara blinks. “What?”
“I’m trying to stay away so I don’t jump her bones right here in front of everyone.”
There’s a long, horrified beat.
“Oh my Rao, Y/N!” Kara nearly drops her cupcake. “Ew! Just—ew, okay? TMI!”
She springs up from the couch like it burned her, wiping her hands on her dress like she needs to physically scrub the mental image away.
You can’t help the grin tugging at your lips. “You asked.”
“I was expecting, like, ‘We had a fight,’ not graphic horny sibling confessions!”
You shrug, cheeks hot. “It’s not my fault Lena decided to wear that dress. Look at her bu—”
“NOPE,” Kara groans, clutching her head like she’s been cursed. “I’m done. I’m going to go talk to literally anyone else.”
She storms off in mock horror, cupcake still in hand.
You shake your head, trying to laugh it off, but the heat under your skin doesn’t go anywhere.
Across the room, Lena catches your eye again. She quirks an eyebrow—teasing, knowing. Like she knows exactly what just happened. Like she knows exactly what that dress is doing to you.
And then—she moves.
Not toward you. Not yet.
But toward the music, toward the open space where a few others are swaying lazily in pairs. She doesn’t say a word. Doesn’t invite anyone to join her. Just starts moving like the music is something she owns.
You can't believe your eyes, you can't believe she is dancing. Because Lena doesn’t like dancing. At least, not usually. She’ll do it if she’s drunk, or if you put on music in the morning and pull her close, swaying your hips together in lazy half-steps across the kitchen floor.
But this?
This is something else entirely.
She moves like a secret meant only for you—hips swaying slow and deliberate, head tilted just enough to let her braid slide over one shoulder. Her eyes flick toward you again, dark and dangerous and amused.
You don’t mean to stare. Honestly, you try not to. But your eyes betray you—again—and when hers find yours from across the room, she winks.
Your entire face goes hot.
Kara, who somehow always appears at the exact wrong time, leans in with a low, exasperated warning: “Lena, please don’t do that. She’s already having a really hard time with that dress. Let’s try to keep it in our pants, okay?”
Lena bursts into laughter like Kara’s just delivered the punchline of the year. She turns toward her, voice sweet like honey and just as dangerous, “Oh, that’s exactly where she’s going.”
“Why! Why are you two doing this to me today?” Kara groans, visibly scandalized. She takes a few bold strides toward you like she’s about to stage an intervention. “Hey, horndog! Can you and your girlfriend behave? No one here wants to see you staring at each other like that.”
You try to play it cool, coy, anything to hide the panic rising in your chest. “Like what?”
“Like the world is going to end if you can’t touch each other.”
And it’s… too accurate.
Your breath catches. Your eyebrows lift, surprised—shocked—that she said exactly what you’re feeling, like she cracked open your chest and peeked inside. You blink, fast, but it’s no use. The tears come anyway. Hot and heavy. Because maybe the world is ending. Maybe it already did.
“Shit,” Kara mutters, instantly worried. “Shit. Sorry, Y/N. I didn’t mean to yell.” She softens, crouching beside you like she’s apologizing to a child. “Please don’t cry.”
You swallow, throat burning. You have to tell her. You can’t keep lying, not to her. She’s your sister. She’d understand. She'd keep your secret for tonight, you're sure.
“Kara, I—I gotta tell you something.”
But before you can get the words out, Lena’s already beside you, like she felt you slipping.
“Hey,” she says, soft and steady. “It's okay.” She glances at Kara and gives a subtle nod—dismissal or protection, you don’t know which. “I got her.”
Then her eyes are back on you. Warm. Calm. Still yours in a way that wrecks you.
“Come on, honey,” she whispers, reaching for your hand. “Let’s go clean your face.”
You let her pull you to your feet.
And you don’t look back.
The bathroom is warm and quiet, and thankfully far from everyone. Lena shuts the door behind you with a soft click, and you don’t say anything at first—just grip the edges of the sink, trying to breathe.
She dampens a towel, dabs gently under your eyes, her other hand cupping the back of your neck to steady you.
“You okay?” she asks, voice low.
“No,” you answer. Too fast. Too honest. “But thanks for pretending I am.”
Lena offers a faint, tired smile. “It’s what we’re both doing tonight.”
You flinch. “Right. Guess I just wasn’t as good at it.”
She shrugs, still impossibly calm, like she’s not the one who sent your entire nervous system into overdrive five minutes ago. “You weren’t supposed to be good at it. Just play the part.”
“Oh, I was supposed to play the part?” You scoff. “You’ve been swaying your ass around the living room like you’re trying to win a lap dance contest.”
Lena raises an eyebrow, unbothered. “I wore a dress. I danced.”
“You winked at me.”
“You stared.”
You push away from the sink. “Oh, come on. You did it on purpose even though we had a deal.”
“I didn’t even touch you, Y/N.”
You step closer, until there’s barely space between you. Close enough to feel her breath. Close enough to fall. “You know you don’t have to. Just admit that you wore this dress for the sole reason of driving me insane.”
She meets your gaze—unflinching, infuriating, impossible. “Maybe I did.”
And that’s it. That’s the moment.
You push her back against the wall—not rough, not gentle, just enough—and you’re kissing her before you even think it through. You kiss her like you’re furious. Like you’re starving. Like this is the last thing keeping you alive.
And when your tongue brushes against hers and you do that thing—the one you promised you wouldn’t do—Lena gasps into your mouth, like it knocks something loose inside her. But she doesn’t stop you. She pulls you closer.
It’s not gentle. It’s not careful. It’s not pretend.
It’s hunger. It’s grief. It’s home.
It’s everything you’ve been trying to bury.
She tastes like red wine and regret, and the kiss feels like confession—hot, reckless, holy. A sin you’d commit again. A sin you'd commit forever if it always led to her.
Your hands are in her hair, her fingers are tugging at your shirt like she can’t bear to let go, and for a split second it feels like time is folding in on itself—like this isn’t borrowed or fake or ending.
When you finally pull back, breathless and trembling, her lipstick is smudged, and your heart is thundering so hard it hurts.
Lena blinks, stunned. Her lips part like she wants to say something, but the words don’t come.
“I wanna rip this goddamn dress off,” you whisper, and it’s not just lust—it’s desperation. Worship. Grief.
Her breath stutters. “Don’t. Don’t say things like that, if you're not gonna do it.”
But her voice is barely there. She’s flushed and on fire, her chest rising and falling too fast, her hands still curled in your shirt like she’s afraid to let go.
You know exactly what you’re doing to her. You also know that she’s doing it to you, too.
You look into her eyes—really look—and it nearly shatters you. Her pupils are blown wide, her gaze frantic, like she’s seconds away from coming undone. Like she’s begging you to give in first so she won’t have to.
And for a second, you almost do.
Because why does this feel like how the world ends and how it begins, all at once?
Why does it feel so right—so yours—but also borrowed and sinful, like something you were never meant to hold this long?
She nods at you slowly—like permission. Like a plea. Like please don’t stop, please keep going, please touch me.
And you understand. You know what she’s asking for. What you could have, right now, if you just reached for it.
But you can’t. Not when she isn’t yours anymore. Not when her body remembers you, but her heart already said goodbye.
You take a step back. Barely an inch, but it feels like an ocean.
“Lena…” you whisper, and your voice is wrecked. “We said we wouldn’t.”
Her eyes flutter shut. She nods again, this time with her jaw clenched tight like she’s trying not to fall apart. “I know.”
You adjust her dress carefully, smoothing the fabric where your hands had bunched it. And she lets you.
Silence settles between you, thick and awful.
You just stand there, in the eye of the storm, hands still aching from not touching her, mouth still bruised from the kiss that wasn’t supposed to happen.
“I’m gonna—” You gesture vaguely to the door, already backing away. “I just… I need a minute.”
You don’t wait for Lena to answer. You can’t.
She looks wrecked—lip bitten raw, dress rumpled, chest still rising like she hasn’t found her breath yet—and you know she’ll need time to pull herself together before walking back into that living room like nothing happened.
So you do what she doesn’t have time to. You flee.
You make it back into the hallway with a drink in your hand and a practiced smile that you hope doesn’t look like a bruise.
Kara shows up beside you not much later, “I don’t wanna know what happened in there, I just wanna make sure you’re okay.”
You force a grin, bumping her shoulder. “Relax, Kara. You didn’t break my heart just because you called me a horndog.”
She gives you a look, but there’s relief in it.
You look down at your glass, trying to shake off the way your ribs still feel like they’re cracking open. “By the way,” you add, voice lighter than your chest feels, “I thought you said there would be cake?”
The party winds down slowly, like the end of a dream you don’t want to wake from but can’t stay in, either.
Lena doesn’t say much when she comes back from the bathroom. Her lipstick is fixed, her expression unreadable. You don’t look at her. Not at first.
You just stand beside her when the final toast is made, you hold her hand when Eliza pulls you both in for a hug, and when Alex thanks everyone for making the night so magical, you smile like your heart isn’t dragging behind you in pieces.
You don’t say anything until you’re alone again, walking Lena to her door, the city silent around you like it knows what’s coming.
“That kiss—” she starts, unlocking the door slowly. “That wasn’t fair. To either of us.”
You nod. “It was the wine. The dress. The whole romance-in-the-air thing.”
She swallows hard. “Yeah. Just... a mistake.”
“Right.” You try to believe it. Try to make it sound like you mean it.
She doesn’t ask you to come in. And you don’t ask if she wants you to. Just a nod. A quiet goodnight. The slow closing of a door that feels way too familiar now.
The next morning, your phone buzzes.
You’re still half-dreaming when you reach for it, fingers fumbling across the nightstand. Your body is heavy with exhaustion, with memory. The space beside you is cold. Of course it is.
The screen lights up.
Nia Nal sent a photo.
You tap it open without thinking. And then you stop breathing.
The picture is from last night—softly lit, slightly blurred, but unmistakable. It's you and Lena.
Neither of you looking at the camera. Just… looking at each other.
You're halfway through a laugh, your smile crooked and helpless. She's watching you with the kind of expression that makes time stutter—like you’re the only real thing in the room. Like you're gravity itself.
And underneath it, Nia’s caption reads:
Find someone who looks at you like you're their whole world 💫 #relationshipgoals
Your heart twists. Violent and sudden.
You press a hand to your chest like that might steady it, but it doesn’t. Because this isn't some cute picture. This is a mirror. A gut punch. A truth you’ve been too afraid to say out loud.
What are we doing? Why are we pretending we can survive this apart?
You’re already flying before you can stop yourself—barefoot, breathless, wind slicing at your skin. You don’t care. You’d fly straight into the sun if it meant seeing her again.
You land on the balcony just as she reaches for the handle.
The door flies open, and there she is. Hair unbrushed. Eyes rimmed with sleep and something deeper, something unraveling.
She stares at you like she isn’t sure if you’re real.
“I was coming to you,” she says, and her voice is nothing—just breath and want.
“I know,” you whisper.
And that’s all it takes.
You crash into each other like gravity won. Like longing built too long inside your bones and finally broke free.
Her hands are in your hair, yours on her waist, your mouths finding each other in something too fierce to be gentle, too soft to be violent. The kiss is everything you didn’t say. Everything you couldn’t.
You taste grief and love and every second of pretending. You kiss her like you’re trying to memorize the shape of a future you nearly gave up.
She kisses you like she’s trying to say sorry without words. Like don’t let me go again.
You pull her closer. Like you're trying to tell her that it's going to work this time. We'll make it work.
You both shake, slightly, from the weight of it.
And when you finally break for air, foreheads pressed together, hearts slamming in sync, you whisper what’s been sitting in your chest since you saw that photo, “I look at you like you’re my whole world because you are.”
Her breath hitches.
And then she’s kissing you again—fiercer this time. More certain. Less fear.This time, it’s not the party. It’s not the wine. It’s not a sin, nor a secret. It’s real. It's yours.
