Underswap Stories

1.2K Stories

Hidden for so Long (Sans AU x Reader) {Remake} by RandomWriter-Chan
#1
Hidden for so Long (Sans AU x Read...by Just Here & Thinking
Long ago, two races ruled the Earth: HUMANS and MONSTERS. One day, war broke out between the two races. After a long battle, the humans... wait no, the monsters were vic...
Unexpected Helper (Nightberry) by SpiritWolfNura
#2
Unexpected Helper (Nightberry)by Kyran Wolfe
Blue is sick of being treated like a child by his friends and family. He shoves down his negativity in order to stay 'happy' like they want though. Nightmare has had eno...
Completed
Karmatic Trio (Bad time trio x BNHA)  by DontAskImN0body
#3
Karmatic Trio (Bad time trio x BNH...by ImN0body
This story takes place after the player vanishes from their fight with the bad time trio aka Sans, Shift, Stretch. The three got stuck there for a very long time until a...
He is too good...(Dustberry) (Blueberry x Dust) by fuglyduck
#4
He is too good...(Dustberry) (Blue...by Sabbie
This story will contain allot of violence, cussing, smut and other things... Blueberry used to hangout with Ink, going around visiting different AU's ..However when they...
Black Roses (Overprotective!Bad Guy Sans' x Child!Reader) by JulesRedenger
#5
Black Roses (Overprotective!Bad Gu...by JulesRedenger
Nightmare found a young child a long time ago. When they fell into a coma it sent him over the edge. several hundred years later the child wakes up in a castle of darkne...
Completed
A Miscalculation In Space by Readern111
#6
A Miscalculation In Spaceby Readern111
He knows he'll be dooming them if he falls, but he's tired, his body is breaking apart, held together on a higher being's whim only. He wonders if there'll be another to...
Six Skeletons, One Maid by RaccoonSinQueen
#7
Six Skeletons, One Maidby RaccoonSinQueen
Moved from AO3 because of reasons! "You are the only maid (or worker in general) that serves for the Skeletal Household. It's a skele-ton of work, but you manage by...
The Story of a Reaper [COMPLETE ✔] by tRaSh_4U
#8
The Story of a Reaper [COMPLETE ✔]by Undertale_tRaSh_4U
When made by his father, the god of death, he didn't know his purpose. All he could do was kill things on accident...he didn't mean to kill them, he just wanted a friend...
Reborn as fellswap san and now I'm kinda blind!? by KarmaAkabane425
#9
Reborn as fellswap san and now I'm...by Karma Akabane
What if..someone from our world was reborn as fellswap sans? But an accident when he was young leads to becoming blind for a long time and papyrus feels guilty about not...
AU Sans X Reader One-shots by Little_Blue805
#10
AU Sans X Reader One-shotsby Blue
Completely female readers unless a request asks different. That's...really about it, enjoy!
Becoming Error, The Forced God Of Destruction by PinkieKidoCup
#11
Becoming Error, The Forced God Of...by PinkieKido Cup
What if someone is reborn as Error? What if they aren't so bad? What if they're suffering in silence and keeping their job a secret for fear of hate? How will Ink react...
A Skeleton's Hope (Undertale AU's x Reader) DISCONTINUED/BEING REWRITTEN by Just_Vibing_Man
#12
A Skeleton's Hope (Undertale AU's...by Dead
Sans and Papyrus were your best friends until randomly they just cut off all contact with you. This went for everyone else in your life so it didn't really hurt that muc...
Undertale x male reader by RandomKid362
#13
Undertale x male readerby Toad Yeager
So harem book of Charas and Frisks x male reader but real description is below this. The only one of his person in all universes is part of Undertale with an OP powers b...
New Purpose (US!Papyrus x Female!Reader) by OreoDaSkeleton
#14
New Purpose (US!Papyrus x Female!R...by ~Oreo~
Y/N, meets a new coworker that changes her life forever. A monster, doing his best to make a living after moving out of the underground. Sans is this ecstatic, cheerful...
Criminal Conflict (An Undertale sanscest story) by __Purple_Fluffball__
#15
Criminal Conflict (An Undertale sa...by Crossmare
This is an Undertale book Criminals have always littered the streets causing a mess and breaking the law. But what happens when criminals Fall in Love? This includes all...
Completed
The One Thing That They Care About (Sans AU x Reader x Papyrus AU) by voltimer
#16
The One Thing That They Care About...by 𝐜𝐡𝐫𝐨𝐧𝐨𝐬, 𝐭. 𝐯.
Y/n L/n. A special human with a special SOUL. Yes, her Soul Trait is something new. But other than her SOUL trait she has another secret. One day, while she was at the...
Completed
AU Sans x Reader Oneshots by MorningSweets
#17
AU Sans x Reader Oneshotsby {sweets}
**PLEASE NOTE** -Cover art does not belong to me, I will only take credit for the stories, I do not take credit for characters. -I will not do any lemons -This is my fi...
Completed
My Anomaly (An Error Sans X Reader)  by nightmare597
#18
My Anomaly (An Error Sans X Reader...by Nightmare
When your sibling Chara goes missing you fear the worst, but life takes a surprising turn for the better when they release the monsters trapped underground. Living this...
Ulty: A God's Birth by Ultimateashes
#19
Ulty: A God's Birthby Ulty Dust Sans
Official remake of Ulty: Creation of a monster A story that starts from Dusttale and goes around the AUs, completely transforming our protagonist English is not my nativ...
Completed
Naturetale : reborn as lavender  by KarmaAkabane425
#20
Naturetale : reborn as lavender by Karma Akabane
(As far as I know, no one has made a story about naturetale like this so..and the only reason why I writing one like this is because of fatal error part 5? Or part 4, go...