1 - 20 of 99 Works in Alternate Universe - Undertale Fusion
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Ever since the Monsters were sealed away to the Underground after the war, Spamton had tried his hardest to live his life without his monster husband by his side. But memories weighed heavy on him, unable to let go of the past and the future they were supposed to have together.
So, for the small chance of seeing him again, Spamton leaves it all behind and makes the jump.
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We All Have Tales by ThatWiseOwl
Fandoms: Deltarune (Video Game), Undertale (Video Game)
23 Sep 2025
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Just their luck to break their fall on top of those pretty yellow flowers get a 'minor' concussion and be taken in by a tall goat monster and her barely tolerable skeleton roommate. It could be worse, if the mean purple lizard monster and the anxious deer ever decide to quit trying to kidnap them.
Deltarune/Undertale AU - What if Kris fell into the underground years after an abandoned neutral route, where a fishy empress is out for human blood for killing their best friend.
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The Quiet & The Ringing by HighQualityGohanFigurine
Fandoms: Vocaloid, UTAU (Audio Database), Undertale (Video Game)
19 Sep 2025
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Finding herself alone, Akita Neru sits near the edge of the cliff and calls Kasane Teto.
Nobody will ever pick up.
- Language:
- English
- Words:
- 370
- Chapters:
- 1/1
- Kudos:
- 4
- Hits:
- 77
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The Forsaken and the Cherished by stitchthelilo for thovcs
Fandoms: Forsaken (Roblox), Undertale (Video Game), but not a crossover kinda situation
07 Sep 2025
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Summary
Seven was confused.
Seven was really confused.
As the Destroyer of Creation, he had a very important job to do every day; keep the balance of the Multiverse, and make sure there were never too many AUs being made. He used to love the job, as it fulfilled his sadistic pleasures - but even now, despite those same looks of fear, he saw it more as a chore than a way to vent out his frustration and violent urges. After a couple centuries of doing the same thing, anyone could get tired of it. He never allowed himself to feel bad, though. Emotions were bad for the job.
But, because he was the Destroyer of Creation, Seven always looked out for AUs to destroy. Sometimes he came across empty AUs, but he never paid any attention to them because there were never any residents.
This time, there was.
OR
When the Destroyer of Creation - Seven - discovers across a lost child in a blank AU, he’s forced to take him in and raise him as his own. Sometimes, he feels as if this is how things were always meant to go.
Only problem is.. he lacks any code.
P.S; This is not a traditional crossover fic, this is a fic where 007n7 is in the role of Error Sans, and Chance is in the role of Ink Sans.
Series
- Part 3 of Longfics
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Summary
“There used to be two boys I hung out with,” Nagito tells her. “They were twins. Hajime and Izuru. I didn’t know their circumstances, but we knew each other.”
The snow is cold, in snowdin. Chiaki shivers into her kitten hoodie, watching Nagito as he watches the distance. “I think you would have liked them.”
“What happened to them?” Chiaki asks him.
He turns to her, smiling, “They fell down. It’s— a natural illness of monsters, sometimes. A state close to death, what you humans call a ‘coma’. They were taken by the royal scientist and her assistant. They were as good as dead anyway, so it didn’t seem like a problem that they would be used in research to break the barrier.”
Chiaki shudders, “So they… They’re dead?”
“See, that’s the thing,” Nagito says. “We never got their dust back.”
[KomaHinaNami Week 2025 Day Six: Fantasy AU/Other AU.]
Series
- Part 3 of forwards, beckon, rebound (Undertale/Multifandom Crossover)
- Part 6 of KomaHinaNami Week 2025
- Part 137 of crossover works
- Part 111 of danganronpa crossover works
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suicide plans by Buttercup_ghost
Fandoms: Kagerou Project, Mekakucity Actors, Undertale (Video Game)
14 Aug 2025
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Summary
“So you also had a plan with your sibling to save your family?”
Ayano blinked red eyes at the young child in front of her. Their eyes were also red, scarlet painted over babydoll brown. The Daze, or the void as the kid was affectionately calling it, was split in half between them and her.
“I- yes, I suppose,” the kid, Chara, said. “But I doubt yours was like mine. I- kind of killed myself for mine.”
They blushed, contrite, as if this was a small mistake and not their life. Ayano laughed, decidedly nervous.
“Ah, you’d be surprised…”
Series
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Shen Yuan’s Underground Adventure by RoseCrawford
Fandoms: 人渣反派自救系统 - 墨香铜臭 | The Scum Villain's Self-Saving System - Mòxiāng Tóngxiù
14 Aug 2025
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Summary
“Well?” The ghost snapped. Shen Yuan jumped at the harsh tone, before hissing at the pain that brought. The ghost rolled his eyes, pointing at the jar. “That’s to heal you! Get on with it!”
Even with the yelling, Shen Yuan didn’t move for a long, long moment after that. He simply stared at the ghost, taking in his fancy looking robes, his angry face, the way that he was completely see-through.
And then, with all his heart, Shen Yuan said softly, “What the fuck.”
—————
Or, Shen Yuan did not mean to fall into a world of drama-looking people, but now he has to find a way out if he ever wanted to go home again. If only the people he met along the way would stop trying to kill him!
An Undertale SVSSS fusion, but no knowledge of Undertale needed.
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through the cold and bitter haze by CaveDwellerTogore
Fandoms: Sonic the Hedgehog - All Media Types, Undertale (Video Game)
07 Aug 2025
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Summary
They had a plan.
One that would free everyone.
But... could he do this? Could he hurt innocent people?
Could he stand to let them be consumed by bitterness like this?
Series
- Language:
- English
- Words:
- 837
- Chapters:
- 1/1
- Kudos:
- 4
- Hits:
- 24
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Summary
(An AU were the cast of Murder Drones take that place of the Undertale Cast.)
After Uzi falls into the Underground, she must make her way through, learning more about herself along the way.
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the second & third human. by Buttercup_ghost
Fandoms: Mahou Shoujo Madoka Magika | Puella Magi Madoka Magica, Undertale (Video Game)
25 Jul 2025
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Summary
*A pair of beautiful dolls. Keep together. Do not separate.
Series
- Part 2 of forwards, beckon, rebound (Undertale/Multifandom Crossover)
- Part 131 of crossover works
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there are eight humans. there are eight souls. by Buttercup_ghost
Fandoms: Undertale (Video Game), Mahou Shoujo Madoka Magika | Puella Magi Madoka Magica, 文豪ストレイドッグス | Bungou Stray Dogs, Dangan Ronpa Series, Persona 5
25 Jul 2025
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Summary
The First Human. Whether they be angel or demon, it depends on you.
The Second Human. Believed by the humans to bring salvation to the world, yet unable to fulfill that destiny as it would mean leaving her dearest friend.
The Third Human. She has the potential to become a Devil even more wicked than any.
The Fourth Human. Will she remain blind, or will her unbending back guide her to the correct answers?
The Fifth Human. An empty tool that does not know what it means to be human, much less monster.
The Sixth Human. A brightly burning soul of justice fed up with the hand dealt to him.
The Seventh Human. For how can you stand up for justice without being brave?
The Last Human. The one with the power to save or damn them all.
STAY DETERMINED.
Series
- Part 1 of forwards, beckon, rebound (Undertale/Multifandom Crossover)
- Part 106 of danganronpa crossover works
- Part 130 of crossover works
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Summary
“What are you going to do?” She peers at you in concern. “I mean… at the end of this, to get home… you'll have to do something horrible, won't you? If it was me, I'd… I'd have given up already.” She bites her lip, pensive. “But you… You didn't get this far by being pessimistic like that, did you? You have — hmm. Something more than hope. Determination, maybe? Hah. Maybe humans are just built different?” She smiles. “Well, I don't know either way. I do think its incredibly, though.” She huffs another laugh. “Touko would make fun of me, but… I think… It's almost like something from anime. You humans—you make such wonderful shows. I guess… before now, I always thought… that they were just shows? That it wasn't real. That—that grit, that optimism, that hope, that… determination. That none of that was real. Just a fancy, made up lie.” She sighs. “Haaaah.” Then she smiles. “You made me feel differently. You made me believe.”
(A dinner with Komaru Naegi.)
Series
- Part 3 of keep pretending to be one.
- Part 124 of crossover works
- Part 103 of danganronpa crossover works
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Summary
“I hate you,” the flower told him, once.
It was plainly stated. Like a simple statement of fact. It didn't even sound bitter, or resentful — just tired. He hummed back, just as unbothered, smiling still.
“I know,” he said. “I hate me, too.”
Series
- Part 2 of keep pretending to be one.
- Part 101 of danganronpa crossover works
- Part 122 of crossover works
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Summary
I want to tell you a story, I think. But the words are like shards in my throat.
Once upon a time, I could start, there was a girl that hated everything.
Once upon a time, I could continue, there was a boy who didn't.
But it didn't matter, did it? No matter how I told the story, the ending has already been written.
Series
- Part 1 of keep pretending to be one.
- Part 100 of danganronpa crossover works
- Part 121 of crossover works
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Galovania by Dpgames177
Fandoms: Pocket Monsters: Scarlet & Violet | Pokemon Scarlet & Violet Versions, Undertale (Video Game)
26 May 2025
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Summary
"You've been busy aye, lad?"
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SIkuna's Guide to Undertale by Anonymous
Fandoms: Undertale (Video Game), 呪術廻戦 | Jujutsu Kaisen (Manga), 呪術廻戦 | Jujutsu Kaisen (Anime), Canon? We Don’t Know Her (Discord Server)
15 May 2025
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Summary
It takes a few blinks for his eyes to adjust.
The slightly-sweet smell of pollen, the warm softness beneath his palms and brushing his cheeks, filters through his awareness as his eyes flutter open. He squints against the dim amber light that pours in from a hole in the cavern ceiling far up above him and, for a while, he dazedly watches dust motes shimmer and dance as they’re caught in the rays.
It’s quiet. Vast and cavernous, pale stone walls decorated with lichen and the odd bit of moss, harsh edges softened and smoothed over by the trickling rivulets of golden spilling sun. Nikita pushes himself upwards, head pounding as his limbs tremble, and ah.
Welp. He fell.
AKA. The fic where 15+ authors shove their Sukuna self-inserts from Jujutsu Kaisen into Undertale. For funsies!
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Summary
Adam is approaches the biggest challenge of his journey yet. Facing the King... but his nerves get better of him.
To help him, Lucifer decides to tell him a story of a long ago... the tragic tale of first fallen human and princess of Underground.
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HarmonyTale by Soul (orphan_account)
Fandoms: Chonny's Charming Chaos Compendium Vol. 1 - Chonny Jash (Album), Undertale (Video Game)
22 Dec 2024
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Summary
Giggles and twirls hair... Undertale au.. No idea if this has been done before..
Series
- Part 1 of Jashverse in Aly's old fandoms <3
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to take a journey through the snow by frydazed
Fandoms: Super Dangan Ronpa 2, Undertale (Video Game)
18 Dec 2024
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Summary
Hajime had to wrap his arms around himself as he trudged onto the snowy path. He only had some dead kid's ribbon stashed in his pockets, and like hell that could do something against the howling snow in the air. He was walking on a path surrounded by a dense clump of trees, blocking out the light.
He eventually saw a bridge in front of him, and a silhouette blocking the path.
Hajime swallowed. He was going to meet real monsters now, and not just the ones Sonia had taken in the Ruins.
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waiting, waiting (just for you) by WalkingWeirdmageddon for GopherGal
Fandoms: Team Fortress 2
31 Oct 2024
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Summary
An alternate ending to the events that took place the day before Morning Cuddles and Afternoon Dates.