Underswap Stories

Trauma is a powerful thing, and not something to be taken lightly. Especially if your "best friend" is the cause of it. But friendship, understanding, and love...

(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...

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...

This is a story before the last human fell around the time Chara was still alive and well. Humans were not being hunted till the adopted prince's passing, however with a...

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...

What if someone died and became the tree of feelings from dreamtale? Well things won't stay the same, that's for sure. (Different everything etc, different personalities...

THIRD TIME IS THE CHARM! [Highest ranking #98 in fanfic] NO IMAGES R MINE

Y/n was and/or is a very sweet child, unfortunately for them they weren't treated very well by their mother or father, Y/n was abused and didn't have anyone. Fortunately...

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...

I found this pictures on deviantart,pinterest,google and Frans Amino

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...

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...

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...

The story of the unstable verse and the new destroyer post exudes. Fresh 404 is learning what it takes to do Error's job. The originals council is learning to face their...

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...

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...

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...

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Hi guys! First of all I should mention that the story pic isn't mine and of course Fellswap belongs to its original creator. A young hiker, Y/N gets lost and accidental...

Humanity is divided over one thing---the Monsters' reappearance. Some believe that they should stay aboveground, and others think that they should be sent back to where...