#because i wanted undyne dreemurr au but. prequel characterization for undyne (13 year old) and chara (19-20 year old)

[smells-like-mettaton]

23 with Chara and Undyne?

Rating: T Word Count: 1621 Prompt: "Carrying the weight of the world" Read on AO3: here

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“No! I'd never doubt you, Chara. Never!”

Chara barely hears the words over Asriel’s snoring. But their bed is the closest to the living room. The walls, made of porous Snowdin wood, aren’t that thick.

“Y... yeah! We'll be strong! We'll free everyone.”

They creep out of their bed. After ten years, they have the most silent path memorized, and their bare feet touch no creaking boards.

“I'll go get the flowers.”

Their heart pounds and pounds. At the words. At the memories. At the thought of who might be watching that video, that video they told Asriel to burn, because if Mom or Dad see it—

It’s not Mom or Dad.

Sitting cross-legged on the rug, camera in hand, is Chara’s little sister. Undyne. Somehow, that’s worse.

“Hey. Kid.”

Undyne leaps up, a crackling blue spear in her hands before Chara can say anything else. Man, was that how they were when Mom and Dad first adopted them? Always hiding knives in the waistband of their shorts, jumping at every noise, hurting themself more often than they’d ever needed to. Not that it mattered. If anything really happened to them, they could just make it un-happen.

Like they already had.

“Chara.” Undyne doesn’t let go of her spear. Her eyes are wide, glowing yellow-green from the magic’s light. “I wasn’t doing anything.”

“Sure you weren’t.” Chara shrugs, sitting down beside her. “It’s rude to take people’s stuff without asking.”

“I didn’t take anything!” Undyne finally lets the spear dissolve into blue sparks, but she doesn’t sit back down yet. She probably appreciates the rare chance to feel taller than Chara. Though Chara imagines it’ll only be a year or two before her natural monster height catches up to them.

“Azzy was showing me how to use his camera today, but it wouldn’t let me record anything on this one” Undyne grumbles. “How was I supposed to know there was already stuff on it?”

“Hm. So that’s why you snuck out in the middle of the night to watch it.”

She winces. She’s not a very good liar, which isn’t surprising for someone growing up with Dad and Azzy. All of Chara’s own subtlety comes from Mom and… well, everything else.

It’s easy to lie when most people won’t believe you, anyway.

Undyne shakes her head, her long hair whipping back and forth.

“You’re just upset because I know what you were going to do.”

Chara’s heart stops, just for a moment. The whole world seems to freeze with it.

She has to be bluffing. She’s just a kid. How could she have guessed what Chara was willing to sacrifice?

…Then again, Chara had been younger than her when they’d made that choice.

“If you’re so smart, tell me.” Chara looks up, their grin as sharp and intimidating as they can make with boring human teeth. “What was I going to do?”

She meets their gaze. Of course she’s not even a little scared. Their sister’s a tough one.

“You were going to go through the Barrier. You and Azzy. I know how it works.” She crosses her arms, smirking a smug little smirk.

“You don’t know anything,” Chara snaps back automatically. Admitting anything else is unthinkable.

They’re going to steal Azzy’s desserts for the next month for letting Undyne get ahold of that tape.

“Mom says not to eat the yellow flowers. Or any flowers. Everyone knows you got sick doing that once.” Undyne’s brow furrows, despite the confidence in her voice. “I grew up in Waterfall. I’ve read the walls. I know how it works. The only thing I don’t know is…”

“What?” Chara tries not to squirm. They aren’t afraid of a thirteen-year-old. They’ll bribe her or blackmail her into not telling Mom and Dad. But aside from that worry…

It’s almost a relief. That someone else knows. That there’s one less person to lie to.

“Why didn’t you go through with it?” Undyne finally plops down on her knees. “You were already sick! If you’d just… merged with Azzy, and then… and then we’d all…”

Chara blinks. That… isn’t the response they’d expected. In hindsight, it’s obvious how stupid their plan was, but perhaps to a child, their old logic still seems sound.

“We’d all be dead,” they say quietly.

Undyne looks up, but Chara shakes their head.

“We would. Not just me and Azzy. But all of us. Even if Azzy hadn’t fought to spare the humans, even if we’d collected six souls… There’s too many of them, Undyne.”

“What… how do you know?” Her eyes narrow. “I guess Azzy is pretty soft… but it’s not like you even tried.”

Chara laughs. A low chuckle that wants to rise, but they force themself to stop. The last thing they want to do is wake anyone.

“What?” Undyne demands louder. “Okay, maybe Azzy never would’ve worked! But—but I’m here now! You could’ve asked me!”

Chara chokes off entirely. She—she wouldn’t. She’s just a kid.

(It’s not like Chara never asked a kid to kill before.)

“We could do it,” Undyne takes their hands in her smaller ones. “You and me. I know it might be scary to combine our souls, but—but I’d never let you down, Chara.”

Her golden eyes stare into their red ones. Her scales are cold on their skin, but that’s not the reason they shudder.

“No.” Chara meant it to come out firm, but their voice is so small, it’s more like a plea.

“I guess it might hurt, but then we’d be awesome and terrifying so—”

“NO.”

Chara shakes with the force of their breaths. The tape has long since run out, throwing black-and-white static across the floor, across Undyne’s face.

“I… I don’t understand,” she says. “Do you really not want to see the sun anymore? Or do you just not want to… with me?”

“Are you stupid?”

Undyne’s jaw drops. That definitely came out wrong, but the point remains.

“Even if everything went perfectly—which it won’t—you don’t want to be stuck as half a person forever.”

Undyne looks away and shrugs. “Wouldn’t be so bad. I mean, I guess you can be annoying sometimes, but… I always thought you understood. Understood me. So if there was anyone I was gonna be a super cool ultra-boss monster with…”

Chara snorts, ruffling Undyne’s hair. The problem is, they do get it. They really are too alike. No one else would be stupid enough to think that dying on purpose is a good idea, even if she keeps conveniently skimming around that part of the plan.

“Hey. Undies. Look at me.”

“It’s Undyne.” She sticks her tongue out. “Undyne the Undying.”

“Undies the Unpantsing.”

She tries to growl, but it comes out as a laugh. “Shut—shut up!”

“Undyne.” Chara finally uses her real name. They smile. “I do want to show you the sun someday. But it’s… it’s not going to happen by killing anyone.”

“But the Barrier—”

“Someday I’ll die.” Chara shrugs. “Not because I ate some stupid flowers or anything. Just because humans get old faster than most monsters. And by then, probably someone else will fall down here, too. Six someone elses.”

Undyne looks down. “That sounds like a long time…”

“Probably. But, look.” Chara sighs.

Should they tell her? About their power, about everything? She would probably believe them. She trusts them with her life, with her soul. She wouldn’t judge them for the murders they’d nearly committed.

“What I’m about to tell you is a Sibling Secret,” they whisper seriously. “You can’t tell Mom or Dad. In fact, you shouldn’t tell Asriel, either.”

Asriel knows, more or less. He’s the only person that Chara ever told about their power. But the details of why their plan failed��� Chara had never had the heart to tell him. He would’ve blamed himself, even though he’d been right all along.

Undyne’s eyes go wide, but she nods. Chara takes a deep breath.

“I did merge with Asriel. We did go through the Barrier.”

Undyne’s mouth opens.

“We… didn’t get any souls,” Chara continues before she can speak. “But, even if we had. The humans are uncountable. I was stubborn, and foolish. I thought that Asriel and I could defeat them. But could we kill all of them? And when our people rise up to reclaim the surface—would we keep killing humans, forever? Would it be the same war that sealed us all here ages ago…?”

Chara shakes their head. They’re rambling, losing themself in their thoughts. They haven’t even told Undyne what she must be wondering.

“I can go back in time,” they finally say. “So right before the humans killed us, I took us back. I was sick from the buttercups again. I told Mom there was another accident, and they gave me the buttercup antidote. The end.”

Undyne stares, stares, stares. Then, of course, the questions start flying.

“How can you go back in time? Do you have magic? Are you a mage like the kind that made the Barrier? Can you do any other spells? Can you teach me?”

Chara rubs their forehead, but chuckles. These questions aren’t what they expected either, but at least they’re less morbid than before.

“Why don’t you ask in the morning?” They yawn, getting up to eject the tape and press the OFF button on the television. The silence makes it a little easier to breathe.

“...Yeah. Okay.” Undyne stands up, her arms wrapping around her middle. “Hey, Chara?”

“Yeah, Undies?”

“I love you. I’m glad you and Azzy didn’t die.”

“Heh.” They ruffle her hair again. They might as well take advantage of the few inches they still have on her. “Me too, kid.”