Undertale AU Sibling Oneshots

Nightmare x Corrupted! Sister! Reader x Dream!

(yay more angst)

Requested by the lovely MorganLeFox!~

You don't get it.
Why would Dream spend so much time trying stop Nightmare? Shouldn't he spend more time trying to help?
After the incident, you found your brothers too focused on each other and themselves to realize you were still stuck at home, left to watch the tree wither away. The citizens of this place had all fled, so you were left without anyone.
Truly, utterly alone.
A part of you wondered why Nightmare hadn't returned to check out the negativity of this place yet. Perhaps because it was home?
Or perhaps it was the tree, which still bled with positive feelings.
You grew sour at that thought.
That tree.
That damned tree. Everything bad that's happened is because of it!
You looked up at it, finding one remaining black apple at the base. You picked it up, seeing your reflection in it's shiny black surface.
Perhaps... if you ate it, you'd understand what Nightmare was going through? He had to be in so much pain, about as lonely as you are now.
You'd only eat a bit of it, you thought, and maybe convince Dream to do the same.
If Nightmare saw his siblings trying to understand, maybe he'd go back to being good.
Swallowing your nerves, you lifted the apple and took a bit.
Apparently you had blacked out a bit, coming to to find your body screaming in pain, ichor being coughed up, the substance quickly staining your clothes.
You couldn't move as the pain swelled in your back. You could only lay there and wait for it to be over.
You barely heard the voice calling out to you.
"(Y/n)!?"
"Dre—klghh!" You got cut off by another bout of ichor, Dream's hands turning you so you faced him. Horror written plain as day on his face.
"(Y/n)!? Oh god what—? What did you do!?"
"Wanted... to understand..." You choked out, trying to offer him a reassuring smile.
"Understand...? (Y/n), no! That's—"
...No?
No???
How could Dream not see!? How could he not see you wanted to help Nightmare!?
You frowned up at him, no longer hearing what he was saying.
He only cares for himself, your mind hissed, he doesn't want to help Nightmare at all!
You pushed him off and shakily stood, using the tree for balance. "You don't want to help Nightmare, do you Dream?"
"I do! But this isn't how to do it, (Y/n)!"
You growled at him, tendrils shootinh out of your back and smacking into him, sending him flying.
You pick up what was left of the apple, holding it out to him as he stood.
"...Last chance, dear brother. The only way to help is to know."
"There's other ways, (Y/n)! You didn't need to go to such an extreme!"
You scowled at him. "If that's the case, where were you? Either of you!?"
Dream froze.
"You left me here alone! What else was I supposed to do without any way to follow you!?"
"(Y/n)..."
You popped the rest of the apple into your mouth just as Dream reached out. Your tendrils moved quickly, slamming into him again.
Dream coughed as he stood up. "(Y/n), please listen to me!"
"What? And let you tell me even more lies?"
You laughed as he took on another one of your hits. "You don't have the guts to fight back, do you? Too ashamed?"
You lashed out, only to freeze at the last second as someone else moved to block the hit.
Nightmare.
The old Nightmare.
Your brother stood in front of you, uncorrupted. He looked a bit tired, but that didn't compare to the mixed look of pure guilt and regret on his face.
"...Nightmare...?"
"(Y/n), I'm so sorry." He spoke softly, just like before, reaching out to you, "I never meant for this to happen, I—"
You snarled, sending him flying just like you did with Dream.
"Three years..." You seethed, tendrils lashing around you, "Three years I've been left alone. Not a word from either of you!"
You couldn't see their regret, their sadness, anymore. All you saw of your brothers were their own selfish needs and wants.
You turned away, and before either of them could do anything, you used your portals for the first time.

(Have a picture of my baby that literally none of you asked for.)