AN: Not mine.
When I wrote this, I hadn't seen the new episode, so I took a few liberties with the Alex/J'onn flashback scene.
Alex keeps still when she wakes, although it's useless. Kara will be able to hear the change in her heartbeat and breathing that signify a return to consciousness. But she's not ready to dredge up what happened, to admit that Kara was right. God, just the thought makes her feel sick. How can she face her little sister and admit that somewhere, deep down in a place she's tried to deny for twelve years, she resents the person she loves the most? How can she face that without Kara, she doesn't even exist?
"Less thinking, more hugs." Kara's voice is still thick with sleep as she curls closer to Alex. Alex can guess that she probably doesn't want to face the day either, especially after seeing her sister's anguish the night before. "I can hear you thinking."
"There's a lot to think about," Alex says softly. She lifts a hand and curls her fingers into Kara's hair, cradling the blonde's head to her shoulder and nestling her cheek on top of golden hair. Her heart hammers in her chest, dread coiling in her belly. "For both of us."
"I don't want to talk about it." Kara's whisper is tiny, and Alex's heart aches at the sound. Kara's words under the red Kryptonite had hurt deeply, but her remorse and guilt now are even worse. Alex wishes she could take Kara's pain even though she's fairly sure the combined weight of that and what she's already feeling would crush her. But then, since when has she cared about her own wellbeing when Kara's is in jeopardy?
"We need to, Kara. This isn't healthy for either of us. We both have things that have festered...things we need to say." Alex takes a breath. She would rather eat rusty nails than have this discussion. "But first...we need to talk about the letter."
Kara sits up and swings her legs over the side of the bed. She doesn't get up, much to Alex's relief, but it's painful to see how rigid the lines of her body are. "I can't risk that happening again. Next time, there might not be a magic gun to stop me. You know what I can do, Alex..." She chokes back a sob, her hands fisting on her knees. "I don't ever want to hurt anyone again. I thought if I-" She abruptly cuts off. "I wanted to make sure I couldn't."
"Astra wasn't telling me something." Alex's stomach is churning; she hopes in vain that she's wrong. "Something about you leaving the letter here. What was it?"
"Please don't ask me that," Kara whispers, voice shaking.
"Kara," Alex insists, although she feels like she's about to vomit. "Tell me."
Kara's silence is all the confirmation she needs.
Alex hunches over, her head between her knees as she fights the urge to be violently sick. Tears roll down her face, and she can't help but wonder how she could have let Kara down so badly. "I'm-"
"Alex, no." Kara's arms wrap around her, her chin settling on the brunette's hair. "It wasn't your fault. It was me. I hurt you; I let everyone down. It doesn't matter that my brain was altered. In the end...the red Kryptonite just brought out the worst in me. It was still me." She sniffles. "You're not to blame."
"I should have protected you." Alex squeezes her eyes shut.
"Alex, you couldn't have known! Nobody knew that stuff was up on the roof, and even if we had, it was anyone's guess as to what would happen. Kal called when I was on my way to see J'onn, and he said that no two bits of red Kryptonite are alike. The effects are always different." Kara kisses her hair. "Please, don't blame yourself. You always blame yourself for me."
"You wanted to-" Alex's voice breaks. "I could have lost you. I can't lose my sister..." She wraps her arms around Kara, burying her face into the blonde's shoulder. "I can't..." Losing Kara to the Black Mercy was horrifying, fearing her loss after revealing her part in Astra's (faked) death even more so, but after the whole red Kryptonite episode and reading the letter on top of it...well, it's doubtful she's ever going to sleep again without alcohol. Copious amounts of it.
"I'm here. I'm here." Kara presses her forehead to Alex's hair. "I'm right here. I'm so sorry I hurt you..."
"I can't live without you," Alex whispers after a long silence. "If it hadn't been for Astra last night...I wouldn't be here right now." A violent shudder rips through her as she remembers her reaction, remembers what she was reduced to in a world where her sister didn't exist.
Kara lets out a strangled whimper and tightens her grip so much that it hurts, but Alex could care less. She holds Kara as close as she can, tears streaming down her cheeks. "I love you, Kara. I love you so fucking much."
She doesn't want to keep going, doesn't want to admit her own dark secret, but if she doesn't, nothing will ever be fixed. Alex pulls away from her sister, curling in on herself with shame. "But you were right. Somewhere inside...I resent you. And it's not fair, it's not fair because you're my sister and I would die for you..." Alex sobs convulsively.
Tears gleam on Kara's cheeks, but her voice is steady when she answers. "I would have resented me too if I were you. You said it yourself. You were the star. And suddenly, I could touch them. Alex, I've always felt horrible about how Eliza treated you. Treated /us/. She made you responsible for me, and you shouldn't have had to be. You're not accountable for my actions. You don't have to suffer for me, Alex. That's not what I want. I would rather have Lane inject me with Kryptonite than cause you pain."
"Did you really believe I hated you?" Alex lifts her head, needing to see Kara's face. Whatever the answer is, she needs to know.
Kara swipes at her eyes, shaking her head. "No. No, I didn't. Just because I thought it doesn't mean I believed it."
Alex sobs again, this time in relief, and puts her head back down. Kara's voice breaks the silence a moment later. "Alex, I...you've smelled like alcohol for a while now, but I didn't say anything because...well, I was afraid of what you'd tell me. I guess now I know why. Are you...have you started drinking again?"
Fuck. Her shoulders tense. "That's not your-"
"Alex," Kara begs. "Last time, you-you-"
"Yeah, I remember." Waking up in a jail cell once was more than enough; she's not keen to repeat the experience, even if she did end up getting a job out of it.
"You almost died," Kara whispers, and fuck if her voice doesn't cut like a knife. Or a sword, Alex thinks, remembering how she so easily sheathed that Kryptonite blade in Astra's back.
"I'm okay, Kara." She raises her head slightly, offering her sister a thin smile. "At this point, my liver is used to abuse."
That's the wrong thing to say, because less than a heartbeat later Kara's arms are around her with enough strength to make her bones creak dangerously. "Kara, ow!" Alex yelps, struggling uselessly.
"I'm sorry!" The embrace loosens, but not enough to let Alex pull away. "I just...why don't you take better care of yourself? Don't you know that you matter to me?" The hurt and pained confusion in Kara's voice cuts Alex to the core, and despondently she wonders if a day will ever come where she doesn't cause her sister some kind of distress.
"I don't matter, Kara. You said it yourself: I have no life outside of you. Maybe...maybe I'm not meant to. If I'm here just to protect you...well, I guess I can live with that." Even as Alex speaks, her chest aches, but she pushes it aside. Kara is the most important thing; will always be the most important. Her own life means nothing in comparison, a lesson she's had drilled into her since the age of fourteen.
"I can't!" Kara cries. "I want you to be happy, Alex. You deserve to be happy. Why can't you see that?"
"I killed Astra, Kara. I mean, I let you think I did. I let you believe your last family in the galaxy was dead and I let J'onn take the blame, and I'm the one who woke you from the Black Mercy. In one day, I took your whole world away." Alex wipes her face, although the tears keep falling. "And I did it because I'm weak. I was terrified of losing you. But you don't need me..."
"Yes I do!" Kara pulls back, takes Alex's face in her hands. Her blue eyes are shining with tears, but they're also full of so much love that Alex can barely breathe. "Alex, I became Supergirl for you. That plane...if you hadn't been on it, I wouldn't have done anything. I would have stayed hidden, stayed safe, because I knew it's what you wanted. But when you were in danger, I had to save you, no matter what it cost. And yeah, I love being Supergirl, but none of it means anything if you're not here with me! I watched my planet die in front of my eyes...everyone I had ever loved...losing you would kill me." Kara takes a shaky breath. "You're my family, my big sister and my best friend, but more than that, you're my strength. Alex...you've always been my superhero. I just wanted to be yours too."
That does it. Alex loses what little composure she still has, tucking her face into Kara's shoulder like she had that day in the training room after confessing to Astra's "murder". She cries and cries, great, heaving sobs making her body shake as she clings to Kara so tightly that the blonde would probably have broken ribs were she human. Kara rocks her, soothing Alex through tears of her own as she whispers promises that Alex herself had made so long ago back when Kara was still a stranger to the planet under a yellow sun.
I won't leave you.
I'll be your sister forever.
I love you.
It's a long, long time before Alex is able to speak again. She's utterly exhausted, drained from the effort of crying, but she has to know—"You're not going to try and...do anything, are you?"
Kara shakes her head. "No. Astra convinced me to stay. I'm...I'm still terrified of going off the rails again, but I know if I left...it wouldn't fix things the way I thought."
"I won't let you go." Alex finds Kara's hand, twines their fingers and squeezes as hard as she can. "I won't ever let go."
"Promise?" Kara whispers, sounding so much younger than her twenty-four years.
"Of course I do. Kara, you're my sister, and I love you. No matter what." Alex smiles slightly. "That doesn't mean I'm not still angry as hell at you."
"I know." The blonde snuggles closer to her big sister. "But that can wait until after we've rewatched Homeland, right?"
"You're such a brat." The words are undermined as Alex presses a kiss to Kara's hair. "But I guess we could both use a good old Netflix marathon after yesterday."
"Hey, Alex?" Kara looks up at her.
"Yeah?"
"I love you." The utter sincerity in those three words hurts in all the best ways. "You know that?"
"I know," Alex finally whispers, her throat tight. "I love you too, Kara."
That's how Astra finds them when she deems it safe to finally check on her two favorite humans: Alex's arms around Kara as Kara curls against her, head resting over her older sister's heart. There's something playing on the screen in front of them—one of those annoying pop culture references Alex finds it hilarious to make around her—but what catches Astra's eye is the light in Alex's and the way Kara shrieks with laughter when Alex makes some stupid joke about one of the characters.
She knew they would be stronger together, that they would go into the fire as iron and come out as steel. It looks like now, so do they.