Undertail Stories

377 Stories

Under-Expansion (All characters +18) by NeopolitanWritings
#1
Under-Expansion (All characters +1...by NeopolitanWritings
This is all UnderTale characters expanding in multiple ways. Including: Ass, breast, belly, thighs, and maybe even all (And POSSIBLE cumflation) Some and maybe most will...
A Lusty Dream by Mama-Kit-Kat
#3
A Lusty Dreamby kit Kat
As requested by my readers. This book contains explicit content. Stories that follow with your deepest fantasies about the characters of undertale. I take suggestions dr...
Of a Better World by toast_and_bunz
#4
Of a Better Worldby toast_and_bunz
It's been a while since Horror's world could be considered even remotely kind. But a newcomer drops in, and reminds him that there's still sweetness to be found in life...
It's Not Possible ( Nightmare x Killer ) by jesus_davito13
#5
It's Not Possible ( Nightmare x Ki...by Abomination.
It's almost the end of highschool for Killer, an 19 year old student at a human and monster school on the surface. Killer isn't ready to leave the highschool yet as he's...
Completed
omotale one-shots by WingedWhiteTIGER
#6
omotale one-shotsby Angel
this is full of omotale stories I write please excuse my Shity spelling and grammar this is NSFW I do take requests some fontcest
Don't Reset by Gay4Pain
#7
Don't Resetby I'm okay.
Howdy, this is a flowey X reader thing, I'll try to post often.
"Not Quite Determined" Sans x Human/Monster Reader [COMPLETED] by FloweyTheGrouch
#8
"Not Quite Determined" Sans x Huma...by AsrielAs Flowey
You've lived your life without ever knowing your parents. Despite that you dream big because you don't have much; aiming to become a famous singer and prove anyone who h...
Classic x fell (lemon) by JackPutman
#9
Classic x fell (lemon)by JackPutman
Plz give me suggestions of what to do next and if I don't upload for a while it's because I have important things like school homework and I'm probably thinking about wh...
A collection of bad fanfics by powermittens
#10
A collection of bad fanficsby End my suffering
A contest between friends I'm sorry you had to witness this horrible story.
Completed
Falling in pun with you (Completed fontcest Story)  by Intellectualpan
#11
Falling in pun with you (Completed...by Jessica
A skeleton named Sans falls in love with the only thing that makes him happy, that made him feel complete... his brother Papyrus. But when sans suspects papyrus of falli...
Tangled Strings (An Errink Fanfic) by Artist_Bean_Baby
#12
Tangled Strings (An Errink Fanfic)by Artist_Bean_Baby
The art for the title cover is by Pencil_loves_mm on Twitter! Creation and Destruction able to find a balance and keep peace? ...maybe.
I dunno some Undertale au lemon shit by PopRocksbnha
#13
I dunno some Undertale au lemon sh...by PopRocksbnha
This is just some stuff I came up with at night time. By the way all of the submissive are females because I find it harder to write them as males. Don't know why.
ONLY ONE {Yandere!Sans x Reader} by DancingInThePetals
#14
ONLY ONE {Yandere!Sans x Reader}by *•Pastel•*
Hello! Here is a fanfic that I will write for you people who wanted this but couldn't find any.
undertale one shots-lemons by Lindorica
#15
undertale one shots-lemonsby Lindorica
This is like my other one shot story except with lemons/smut/sin/sex or whatever else you want to call it. It might/will include boy x boy, girl x girl, boy x girl, and...
Adult Frisk +18 by CharaTheLustfulDemon
#16
Adult Frisk +18by Chara The Lustful Demon
What Should I Describe Here? I Guess The Title Already Says Everything so Far
You Make My Soul Flutter by SpareRib_Soup
#17
You Make My Soul Flutterby SpareRib_Soup
Yes another fontcest I know. This is currently a work in progress so please be patient with me. Word average of about 1000 words per chapter
My Dream Is A Nightmare(NaJ!Nightmare × Abused nird reader) by Gasterfrisk2
#18
My Dream Is A Nightmare(NaJ!Nightm...by Ender Girl
It's your first day and you had a black eye because of you dad. You where nerves for school because you where going to Underhigh. And you love sciance but what if that a...
I'm Pickin Up Good Vibratons~ (Undertale Sin One-Shot) by DoodleWritesAThing
#19
I'm Pickin Up Good Vibratons~ (Und...by DoodleWritesAThing
Just a drabble :P This story will include 18+ content, if you're comfortable reading that then move along, but if you are younger than thirteen and still have not had...
A Feeling {DISCONTINUED} by TheSundayBlues
#20
A Feeling {DISCONTINUED}by A Person
You were an orphan, and you had just been taken away from your parents or what's left of them, after that fire that burned down your house you lost three things your par...