Inspired by architect of a whole world's nightmares by suitablyskippy on AO3.

DR1 SPOILERS obviously
this fic owes a lot to "architect of a whole world's nightmares" by suitablyskippy, which inspired my headcanon of how junko and mukuro's relationship was, and pretty much inspired the tone/style of this as well ahaha

theres slight incest and consent issues as in kissing/groping without asking permission

"...Hey, Junko. So, are you coming tonight?"
"Sure. Can Mukuro come too?"
"Who?"
"My sister, dummy."
"Oh, yeah, yeah. More the merrier. See ya!"
"Where is it again?"
"My house, of course."
"Right."
She's forgotten who he is, though.

She flips shut the glittery pink mobile phone, and yells for her sister. "We're going to a party tonight!"

"I can't."
Junko spins around. There, in the doorway, is her antithesis. Poor little Mukuro, who is freckly, plain, and without much personality to speak of, is dressed to kill. Not in the same way Junko is, however. Mukuro wears all black, with gloves and a hoodie to pull over her face.

"Oh, you have a mission tonight? Boring. Ditch it."

"I can't-"

"Ditch it."

"...Yeah."

Hahaha. Junko always gets her way when she puts on the Scary Big Sister voice. "It'll be fun," she says in a singsong way. "We never go out. Sisters' night!"

"I don't like going out."

"Don't be such a fucking hermit, Mukuro. That'll fuck up your brain. And put on something nice to wear, you look like trash."

"I don't know what to wear."

"Do I have to do fucking everything for you? Fine. I'll pick out an outfit."

She stomps up to her room in her five inch heels and throws open the door to her sprawling closet. Whenever she finishes a shoot they always let her keep whatever clothes she wants, so she ended up owning a fuckload. She hates most of them, however. But something ought to look good on Mukuro. It might be funny to dress up her little sister in something tight and low-cut, but it probably wouldn't work. Instead she picks out a pair of shimmering black leggings and a white top with a cat print on it. Plain enough to look like Mukuro's own, but good enough to be seen in public with.
She really does everything in this family.

"Wear this." She dumps the hangers on the kitchen table.
"These are your clothes...?"
"Of course. Don't wear anything you bought yourself when we go out, ugh."
"Last week you told me never to touch your clothes."
"That was last week. Fucking strip already, we gotta go."
"I - I need to make a call. Cancel. Where's this party?"
"Some guy's house - think he lives in Inagi."
"What? That's ages away. How're we gonna-"
"Shut up."
And Mukuro does. She always does, that's the satisfying thing.

They get to the party and everyone's staring at Junko. Someone buys her a drink, someone gropes her, and it's business as usual, it's fun, fun, fun. She likes the song they're playing. The beat is fast and hard, like bullets rattling out of a machine gun. The lyrics are about sex, thinly veiled. That's the kind of sound she and Mukuro can relax to. "We like this song!" she yells enthusiastically, puts her drink down; starts to dance. Mukuro's wrist is gripped tightly in her long, polished nails. She doesn't need to ask Mukuro's opinion. They're a matched pair, right? Whatever Junko likes, Mukuro should like too, right? She doesn't have any reason to be any different. Junko's always taught her sister exactly what sort of person to be, even though she tends to mess up a lot of the time.

Before they left, she put glittery spray into Mukuro's boring black hair, dragged a straightener through it, glued long, dangerous fakes onto her sister's stubby little nails and painted electric blue on them, to match Junko's shocking pink. Junko herself is wearing a black and white minidress, tight to her skin, thick with sweat as she dances in an abstract, personal sway, still with Mukuro held tight in her right hand.

They look, she thinks, smiling pinkly, like a pair of dolls. Bright and painted and pretty and not real, not real at all. Maybe that's why people are compelled to act so strangely around them, as if they're angels or characters on TV. Like this guy does, now. He steps up to her as she's dancing; she's miles taller than him and he's ugly, ugly, ugly as sin, with weird fishy eyes. He doesn't look real at all. She could kill him easily. She knows fifty ways she'd kill him right now.
"Are you Junko Enoshima?" he asks reverently.
"That's right." She simpers like a shark.
"That your sister?"
"Yeah. Say hi, Mukuro."
"Hi." she murmurs, and continues to sway oddly against the beat. God, she's awkward.
"Glad you could make it."
"Oh, is this your party?"
"Yeah..." He looks at her strangely.

"Could you get me another drink?" She wants to pet him, like a puppy. Fetch another pina colada, that's a good dog, and probably spike it with something too, but that doesn't matter - she doesn't drink.
"You're hot." he tells her as he hands it to her. She smiles and puts it down. She knows she's hot.
"My sister is too, right?"
"Y-yeah."
"Want us to kiss?"
"Seriously?"
"Why not? Come on, Mukuro, kissy for your big sissy." There's a strange tingle of nostalgia - she used to say that, she remembers faintly, when they were little, taking baths together, and then would blow raspberries on Mukuro's cheek until her sister collapsed in giggles.

Mukuro doesn't offer her cheek, but doesn't move, either, and stands, continuing to sway, as Junko shoves her tongue down her throat sloppily and grips her boob. The guy is staring like he thinks he's won the lottery. He has a faint erection, though he hasn't himself noticed yet. Across the room, something flashes. Mukuro's flesh is like dull clay beneath her claws. Her sister doesn't feel like anything at all. No shape, taste or colour of her own.

"Do you want a drink, Mukuro? You haven't drunk anything. Parties are no fun if you don't drink." she explains exasperatedly as she stops tonguing her sister.
Mukuro nods.
"Get her a cider, she's not used to alcohol."
This boy would fetch her anything she wanted. She loves that in a man.

Mukuro drinks. She's so unvocal already that it doesn't show in her, but Junko can tell it's got to that sharp little brain of hers.
"You're drunk," she teases unnecessarily.
"Yeah," Mukuro seems to observe.
"Haha, what's it feel like?"
"Not as bad," Mukuro replies faintly. "Last time, I nearly threw up."

"...Come outside. Let's talk."
If Mukuro knows she's in the shit, it doesn't show.
The night outside has turned snowy, and the cold is a shock, a sharp feeling down to Junko's bones. She imagines the chill really doing that, stripping off her flesh until there's only a skeleton left. Pretty.
"'Last time'? What's fucking 'last time'? When were you drunk? You don't drink."
"I- it was after a mission. We went to an inn..."
"Oh, and you didn't deign to fucking tell me, did you, princess Mukuro? Your fucking Majesty?" Junko snarks, digging her nails into Mukuro's pliable shoulders.
"Y-you were in Paris for Fashion Week then, remember? I - you were away a while; I couldn't tell you everything that happened. It would've been boring."
"Aww, you're never boring, sis. Everything you do is interesting to me." Junko ruffles her sister's hair affectionately.
"Are we gonna go home now?"
"Hang on. Did you bring a gun?"
"'Course."
"Right. Some guy took a photo of us kissing before. Get on the roof."
"I- I'm a bit tipsy, I'm not sure-"
"Get on the damn roof. I'm the one who has to do the hard work, pretending to flirt with this creep. Wait until I get him alone."

She leaves Mukuro without waiting for an answer, and reenters the fray. There's the guy with his cameraphone, chatting to a redhead. Doesn't matter.
"Hi," she smiles.
"Um, hi. I was just-"
"Come outside, sweetie. I have a surprise for you."
She leads him by the arm, tracing a teasing circle into his skin with the tip of her long nails. She walks in front, letting him follow the sway of her ass in her short skirt.

Once she gets out into the night air, Junko gives the nod, and in a split second, everything is pain. Nothing but a hissing, screaming burst of pain in her right forearm, and the dope with her has a split second to look horrified before another shot sounds and he falls to the ground instantly.
"Second time lucky, huh?" Junko spits up at the rooftop, ripping a strip off her dress to depress the wound on her arm. She's already stopped feeling the pain, however. She learned to channel out things like that a while ago.
Mukuro's head appears, an adorably worried little frown, as emotive as her sister gets, before she jumps down and grabs the guy's body, hoisting it over her shoulder. "Shit, Junko, I'm so fucking sorry, I mean, I just, I just lost my focus for a second and your arm was around his shoulder - I - shit, I can't be sorry enough-"
"Forget it," Junko laughs. "I'm in a good mood."

"Promise me something, though?" she requests as they begin the walk home in the moonlight, Mukuro heaving the corpse, Junko nursing her gunshot wound. "Smile more. You have such a pretty smile."
"Y-yeah."
"And you should start doing your hair more like mine. When we get to that school, right?"
"Hope's Peak?"
"Mmhmm. Exactly."
"Sure. Anything."