1 - 20 of 3,430 Works in Alternate Universe - Underswap (Undertale)

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  1. Tags
    Summary

    When your creations turn into reality, things were never meant to go well. Both you and your brother turn into the characters that both of you created and dread to be in. An alternate universe full of death and war.

    -----

    You were tired from this. Hell, both of you were. You were placed in the front lines while your brother created dangerous explosives. All of this just to survive, to live for another day. All memories are forgotten of who you once were before this painful life.

    Who knew a sudden mishap of a machine could be a savior for the both of you?

    Language:
    English
    Words:
    13,786
    Chapters:
    7/?
    Comments:
    106
    Kudos:
    475
    Bookmarks:
    142
    Hits:
    5,775
  2. Tags
    Summary

    Where you, as the reader, are Sans. And your best friend is.. Papyrus? And now theres Sans? And Papyrus? And Papyrus and Sans and.. This guy says his name is Dust? And that guy looks like he's covered in gunk, and why is this Papyrus calling himself Stretch?

    Blurb;

    “Do we call each other Sans and Papyrus?” He beats you to the question the moment you open your mouth, startling a chuckle out of you. You walk over to him, draping yourself over his shoulders with a long-suffering sigh. “I guess I could just call you bro. Are you the older of us now?” You blink, looking at him through the mirror.

    No update schedule, I can barely remember to write. Ill try though!

    Language:
    English
    Words:
    35,474
    Chapters:
    9/?
    Comments:
    39
    Kudos:
    190
    Bookmarks:
    46
    Hits:
    2,175
  3. Tags
    Summary

    A collection of my Demon Slayer stories and requests from my Tumblr!

    1. Demon!Sanemi And Period Oral
    2. Yandere!Kyojuro And Demon!Reader
    3. Genya And Cat!Reader
    4. Genya And Demon!Reader
    5. A Slayer, A Woman, A Demon - Giyu And Fem!Reader
    6. Rekindling The Flame, Part 1 - Shinjuro And Fem!Reader
    7. Rekindling The Flame, Part 2 - Shinjuro And Fem!Reader
    8. Rekindling The Flame, Part 3 - Shinjuro And Fem!Reader FINALE
    9. Yandere!Alpha!Kyojuro And Fem!Omega!Reader
    10. Sanemi And Fem!Reader Birthday
    11. Writing A Love Story, Part 1 - Teacher!Kyogai And Fem!Teacher!Reader

    Language:
    English
    Words:
    25,484
    Chapters:
    11/?
    Comments:
    14
    Kudos:
    122
    Bookmarks:
    10
    Hits:
    3,607
  4. Tags
    Summary

    You, a Witch, owned a potion shop in Ebott city where Monsters, Humans and supernatural beings lived in relative harmony. You had once had a chance encounter with two skeletons Monsters but to your surprise, both of them were supernatural beings! Quite rare for Monsters to be. Even though you had a hectic meeting with the skeleton brothers, the three of you became quick friends. The vampire skeleton Sans helped you around your shop when he could while his brother Papyrus, a werecat, came around to show off his partners…? Yeah you thought it was a weird way for him to bring you extra customers but highly appreciated!

    Everything changed when one adorable blue skeleton invited you to a yearly masquerade party and something unlocked inside two skeleton's minds when they saw you getting all nice and comfy with another Monster.

    They couldn't let their beloved witch be taken away now could they?

    Language:
    English
    Words:
    196,934
    Chapters:
    36/38
    Comments:
    140
    Kudos:
    411
    Bookmarks:
    81
    Hits:
    13,553
  5. Tags
    Summary

    The Puzzle Honey Bandits are at it again!

    Their reign of terror must end!

    We all know they are monsters who only burgle other monsters.

    What fiends they must be?

    Who would dare?

    They need to be brought down, by any means!

    Language:
    English
    Words:
    14,206
    Chapters:
    6/?
    Comments:
    30
    Kudos:
    10
    Bookmarks:
    3
    Hits:
    198
  6. Tags
    Summary

    Let's follow Killer Sans in a month of chilling with Nightmare's Gang. Antics will surely ensue, seeing as Killer is a major flirt and Nightmare is not.

    ...And he's also a bit depressed lately.

    Thanks for reading and I love you all.

    Language:
    English
    Words:
    5,942
    Chapters:
    9/?
    Comments:
    6
    Kudos:
    8
    Bookmarks:
    3
    Hits:
    173
  7. Tags
    Summary

    It was the only job you could grab. Along with the apartment-life blues, and your college education still ahead of you, could your setting be any more typical?
    Maybe...if some of your regulars hadn't emerged from several feet underground a few years ago.
    But, darn it, you chose this particular store for a reason, and you were going to show these fascinating new faces in and out your door with a smile that (surprisingly) has nothing to do with the fact that you were getting paid for it.
    Good thing, too, because you might get to make some bone-ified new friends in the process.

    Inspired by several AO3 users (listed in the first chapter notes)

    Language:
    English
    Words:
    257,880
    Chapters:
    31/?
    Comments:
    699
    Kudos:
    2,623
    Bookmarks:
    535
    Hits:
    68,517
  8. Tags
    Summary

    "Oops, careful there. You don't know what could happen if ya slip."
    You’re an Au Traveller who ends up in an alternate timeline known as Something New,
    or as most people call it,
    KillerTale
    You soon realize this and attempt to get out, but the Sans from that Timeline notices you and decides he wants to play a game of Hide 'N Seek.
    But imagine that one day in the distant or not so distant future, the two of you could actually fall in love,
    Will he kill or will he spare you?
    How will his Boss react to his choice?
    All will be uncovered soon...

    Language:
    English
    Words:
    4,635
    Chapters:
    8/?
    Kudos:
    29
    Bookmarks:
    3
    Hits:
    306
  9. Tags
    Summary

    Clover was about to die, they knew this.

    But something refused to let them. And something brought them back.

    But…

    This world they entered was not their own.

    ---

    A glitched reset leads Clover into the Underswap Yellow world, with someone by their side.

    Language:
    English
    Words:
    1,583
    Chapters:
    1/?
    Comments:
    5
    Kudos:
    29
    Bookmarks:
    7
    Hits:
    250
  10. Tags
    Summary

    Twelve chapters of the Sans AU's, starring the Star Sanses! (Told in 3rd person omniscient but mainly focusing on Ink's perspective)

    Thanks for reading and I love you all.

    Language:
    English
    Words:
    4,694
    Chapters:
    5/12
    Comments:
    10
    Kudos:
    6
    Bookmarks:
    1
    Hits:
    129
  11. Tags
    Summary

    You’re six months into your career as an electrician and for the first time in your life, you’ve got your shit together. Go you!

    When the job brings you to a mansion inhabited by skeleton monsters and your ex-girlfriend, things change. The wiring in the house is fried, the skeletons are suspiciously evasive about the basement, and your ex keeps inviting you for sleepovers.

    You just want to get through the repairs without setting the place on fire. Keeping your sanity intact would be a nice bonus.

     

    Or, another anti-harem fic, but in this one, the girlfriend is into you too.

    Series
    Language:
    English
    Words:
    74,170
    Chapters:
    12/?
    Comments:
    613
    Kudos:
    877
    Bookmarks:
    230
    Hits:
    16,488
  12. Tags
    Language:
    English
    Words:
    7,094
    Chapters:
    7/9
    Comments:
    28
    Kudos:
    52
    Bookmarks:
    3
    Hits:
    741
  13. Tags
    Summary

    The color symbolized alot of things once the monsters came to live with humanity. Blue was your favorite color. It stood for stop. It's also a reminder of your ex. Now a skeleton comes at an unstable point of your life. Why does he look so much like your ex Sans? Why does he have stars for eyes?
    And thats the beginning of a crazy spiral of skeletons that don't want to leave you alone. Did I forget this guy calls himself Blue? Love and misunderstandings begin! #this will crash and burn #Enjoy the dumpsterfire

    guess what?! Your gonna get a harem girl!

    Language:
    English
    Words:
    269,769
    Chapters:
    51/?
    Comments:
    304
    Kudos:
    561
    Bookmarks:
    121
    Hits:
    16,516
  14. Tags
    Summary

    Have fun and request away!

    Series
    Language:
    English
    Words:
    7,524
    Chapters:
    31/?
    Comments:
    64
    Kudos:
    10
    Bookmarks:
    2
    Hits:
    967
  15. Tags
    Summary

    After being cheated on by your now Ex Boyfriend (with your best friend no less), you decided to go back to your roots and visit your grandmother. Much to your surprise, she has adopted a gaggle of skeletons who make her big house livelier. Go figure. You might stick around longer, just to make sure these skeletons aren't bad to the bone.

    Language:
    English
    Words:
    114,043
    Chapters:
    23/?
    Comments:
    868
    Kudos:
    1,060
    Bookmarks:
    259
    Hits:
    22,610
  16. Tags
    Summary

    You find yourself sleeping in your car in winter. Being strong enough to get out of an abusive cheating relationship, you opt to sleep in your car rather than be stuck in a bad relationship. While you are wracking your brain to find a solution to your situation, you run into an old school friend and her pack of skeletal boyfriends. Your own situation not being the best, you want to avoid stepping into the situation, however one skelly just can’t let you freeze in the cold. What comes next is a story of betrayal, healing, and helping those that haven’t yet learned to help themselves.

    Mutt didn’t like the human that the rest of his house has as a datemate, what he didn’t count on was ending up falling for the one person that might be able to help everyone in the skeleton household.

    Language:
    English
    Words:
    500,178
    Chapters:
    187/?
    Collections:
    1
    Comments:
    2,131
    Kudos:
    1,650
    Bookmarks:
    301
    Hits:
    75,475
  17. Tags
    Summary

    ~Ava’s Guide to Invading the Multiverse~
    Step One - Go Fishing

    Language:
    English
    Words:
    365,419
    Chapters:
    126/?
    Collections:
    5
    Comments:
    3,283
    Kudos:
    1,925
    Bookmarks:
    231
    Hits:
    47,943
  18. Tags
    Summary

    How many reset can one make out snap.

    Language:
    English
    Words:
    560
    Chapters:
    1/1
    Hits:
    8
  19. Tags
    Summary

    It's been 3 years since we last spoke. And alot is about to happen

     

    Do you wish to

    Series
    Language:
    English
    Words:
    10,337
    Chapters:
    5/?
    Hits:
    36
  20. Tags
    Summary

    This is the wholesome story of meeting your neighbor and learning to appreciate him and his brother.
    Obviously things can be chaotic as you learn some secrets about the pair.
    Can you live with their secrets and your own without falling apart?
    Can you trust them enough to let them see through the cracks in your mask?
    You really hope you should.

    Language:
    English
    Words:
    203,333
    Chapters:
    46/?
    Comments:
    286
    Kudos:
    414
    Bookmarks:
    122
    Hits:
    15,422

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