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Published:
2025-08-08
Updated:
2025-10-29
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2,011
Chapters:
2/?
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truth, warmth, voices, isekai!

Summary:

A culmination of works where the reader gets isekaid/transported into Undertale having been an avid fan beforehand.

Each chapter is a new scenario! Sometimes they might continue off each other while other's might be stand alone, I'd let you know.

Suggestions on scenario's are welcome!

Notes:

(See the end of the work for notes.)

Chapter 1: A New Human (Toriel Helps You)

Chapter Text

It’s like waking up from a dream. What you once knew is over and done with, killed off and deleted as if it had never existed in the first place. 

Your friends, your family, your previous reality fades away entirely. 

In their place is a world you know dearly, somewhere very close to your heart… 

 

A quiet hum echoes around you as something soft gently strokes your hair. The sight of a creature akin to a goat with white fur and warm eyes greet you. The shock of seeing something that isn’t human sends you flying across the room into a wall. 

The monster’s floppy ears and small curved horns poke from her head, and as you come to your senses you realize this monster looks strikingly similar to Toriel from Undertale. Even her robes bear the same color and symbol. 

You feel like you’re losing your mind, is she actually… her? Or is this an expertly crafted cosplay? Maybe you’re hallucinating, or dreaming?

As your mind unfolds you stay glued to the wall. Her snout twitches in surprise, then she takes a stand, stepping away from the plush overgrowth of yellow flowers you had just been laying on.

“Oh dear, forgive me, child. I am Toriel. I promise, I mean you no harm. I discovered you unconscious here. I didn’t want to leave you alone, I hope you don’t mind.” She nervously folds her paws over each other.

Despite feeling like you should be wary, after a few minutes of going through the ruins together you can’t hold your guard up. Everything looks exactly like you imagined it would!

This place that gave you so much comfort in real life, was now right in front of you, being thoroughly experienced in every detail. Even the monsters here look exactly the same, it makes you giddy and excited.

As she leads you further down the ruins, you start to remember things from the game that are supposed to happen. Toriel holds your hand in her warm paw as she leads you through various puzzles with levers to flip and buttons to press. Each one she completes, you silently remember the pattern from countless times playing.  

Later, she pulls you inside her home. It’s plain and simple compared to the rest of the ruins, but lovely nonetheless. It feels like home. 

She introduces you to a bedroom clearly meant for a kid, with toys and small clothes neatly put away. Even so, you don’t hesitate to snuggle underneath the covers and fall asleep almost immediately, you’re more tired than you thought. 

When you wake up there is a plate on the floor that holds a piece of butterscotch cinnamon pie as well as a note from Toriel. Seeing it, for some reason, floods you with indescribable warmth. Gratefully, you eat the pie and savor the wonderful flavors.

You spend lots of time with Toriel in her cottage, but eventually you try negotiating with her about leaving the ruins so you can meet the skeleton brothers. Although, you don’t tell her that part.

Your negotiating doesn’t do much though, she is still adamant that if you want to leave you have to go through her first. There is not a single part of you that can even bear the thought of slashing her down.

Genocide may have been something you tried in the game back then, but it’s different now. Everything is real, she isn’t just a video game character anymore. 

You feel the only choice is to be peaceful, it would hurt too much to actually commit violence with your own hands. 

You know that during this fight, at the doors that lead to the rest of the underground, she won’t kill you. You can choose to stay completely still and in the end she won’t let you die. 

But each burst of magic that hits your soul sends a sharp hot pain through you, it fades quickly, but the lower your hp gets, the pain persists longer. 

Each attack she sends your way you spare her, pleading to end this, that you won’t give up, all the while each cry of pain comes with less and less aimed attacks until she finally brings her arms down in defeat. 

She drops to her knees and grabs you up in a hug. She holds you for a moment, letting her tears subside, until she finally lets you go. 

“I’m sorry, child. But when you leave please don’t come back. I see now that you are strong. When you go out there, King Asgore will try to take your soul. Do not let him. Be strong.”

You nod and thank her for helping you so much. Then she hurries off back where you’d both come from.

Heart full, you proceed through the large doors, excitement brewing in your chest thinking about who you're meant to meet next.

Chapter 2: Unlimited Knowledge (Sans is Snooping)

Summary:

Sans finds/notices things about you and goes snooping to find out more.

Notes:

(See the end of the chapter for notes.)

Chapter Text

You were afraid of getting into encounters, so you asked Sans to let you follow him around just for a little while, so you wouldn’t get into any confrontations. 

The main thing you were afraid of was dying even if it might be possible to respawn, you didn’t exactly want to test it and find out. Sans thinks it’s strange that you seem to know facts about all the monsters in town, things about people you’ve literally never met, let alone never had mentioned to you as far as he knew. Even so, you speak about them as if they had been your best friend.

You’ve become attached to him for some reason, seeking his protection and guidance since the moment you made it to Snowdin and shook his hand. Who knows, maybe him ‘protecting’ you from his brother somehow convinced you that he was trustworthy. But, really, if Toriel had never asked him to make sure you were safe he’d never have allowed you to stay around. 

At first it was somewhat normal behavior, when you were meeting new people your eyes would light up before you’d even get to talk to them, you seemed to be shaking with excitement every time you met someone new. A huge smile on your face. That was odd, but not necessarily bad. He would have assumed that a human first meeting monsters, especially not knowing they existed beforehand, would have been…scared? Or at the very least you’d be wary. But you weren’t, for some reason you did the literal opposite of that. 

Nothing you did made him concerned, maybe confused a little, but not necessarily suspicious. Not until he found a journal you kept sitting closed on the coffee table in front of the couch. You had been living with him and Papyrus since you didn’t have anywhere else to stay, besides the inn that he knew you had no money for, so he let you crash on the couch. Making sure to keep a good eye on you so he and his brother weren’t at risk. 

Part of him knew that he shouldn’t, it would be breaching a new level of privacy that he already was just by taking note of where you went around the underground, but at the same time, he wanted to be 100% sure. What if you had just been pretending to be innocent, and this journal kept your real identity inside. He needed to know, to make sure that you weren’t going to hurt anyone. 

The journal was unassuming, the pages seemed to have water stains on the edges, so you probably fetched it from the dump at some point. The first page seemed like you wrote of your life before you fell down, your family, your job, the school you went to, friends you had, what you had been interested in, simple things as well like your name, age, where you lived. That was odd in itself. Were you afraid of forgetting such basic knowledge?

The pages after that were bizarre to him. Frantic writing about how you were somehow transported into a videogame ‘Undertale’ and a list of things afterwards of what you could remember from your time playing. There were dozens and dozens of bullet points you made of information you couldn’t have possibly known about this place yet. Things that even he hadn’t been aware of, and now felt the need to go check on as soon as possible. Alphys having made artificial temporary souls that were mushed together? Then the information about the CORE…Gaster. You knew about him, despite everyone in the underground being oblivious to the fact. How could you possibly know anything about the man who was literally an anomaly in the universe? 

At this point he needed to take a break. His phalanges were shaking and he was uncertain. You wrote in the beginning about this being a game you were sent to, that had to be the reason you knew so much. 

When he first picked this up, he expected to find mundane diary entries. Not…an account of his entire life, of his world. Things you know span back years and years before you had ever fallen down here. And despite the sick twisted feeling of dread he had, he continued flipping through the pages. 

Not only did you know about Gaster, but supposedly you knew about things that hadn’t happened yet too. Things he couldn’t confirm, but could only imagine were real considering the accuracy of the previous passages. 

You have to be from outside this universe entirely. There’s no other explanation for it. 

He wants to laugh, of course his life is just one big game for other people. Other people he can’t see or talk to. How many lives has he lived where he dies, where someone else dies? 

He doesn’t know what to make of all of this. Instead he just sets the journal back onto the table where he found it, and teleports to his room to think. 

Later, he leaves to check on you, to make sure you haven’t decided to start hurting everyone, when he stumbles on you, Papyrus, and Undyne in the kitchen. He watches as you laugh hysterically at Undyne wrestling Papyrus into the ground to, “SHOW HIM THE TRUE STRENGTH OF A HERO!!!” Effectively getting tomato sauce and pasta everywhere. Despite the chaos in front of him, he tunes it out. Focusing solely on you, reading your stats he notes it’s all the same. 

LV: 1

HP: 20/20

AT: 10 (0)

DF: 10 (1)

Your face is covered with glee, true happiness, not a mask. Because trust him, he knew what a mask looked like after so many years of perfecting his. He could tell you were being genuine. 

It comforted him, but somehow unsettled him all at the same time. The fact that you have so much power. You could abuse it in a heartbeat if you decided to. But you don't, you’ve chosen mercy and kindness. You’ve never hurt anyone here all this time. 

In the journal you also wrote about how you didn’t think he was, “aware of the players ability to save or reset timelines because I haven’t messed with those abilities and have no desire to. Therefore he should have no idea of this ability I possess, the only reason he knew in game was because the player would reset, triggering his machine to go off, or for him to remember something was wrong. I can't allow myself to ever use this power.

So, not only does he have to worry about you having a ridiculous amount of knowledge, you also have abilities that tie back to this game feature that he doesn’t even understand. 

Part of him just wants to be upfront with you and ask. Get it out of the way, and confront this issue with you face to face. But he’s afraid. With how much you know, what if it ends up with him dead? With you getting scared and hurting someone else? He can’t know for sure, and he doesn’t want to risk anything. 

So for now, he’ll just be...observing.

Notes:

Had Respite from Undertale OST playing on loop while I wrote this. I know it’s kind of awkward formatting, it’s too much detail for it to be a concept/blurb/oneshot, but not enough to be a full story right? I dunno, but I think I like it enough to keep writing about it so we shall seeee :3

Notes:

I'm sure this has been done before, but these are things that I enjoy thinking about.
I’d love to write about more scenarios like this, so if you have any ideas feel free to send them my way!
Thank you for reading!