Undertale is owned by Toby Fox and not by us.
Chapter 1
A young person/whatever/determination by the name of Frisk headed up Mt. Ebott on their own for a reason currently unknown other than wanting to see if the stories about monsters are true. As the determination(AN: Determination is one of Frisk's gender pronouns in this fic) climbed up the mountain and found the giant hole in the ground, they paused for a moment; a butterfly fluttered past, capturing the rather tiny child's attention before they looked back at the entrance to the unknown.
They tentatively began to move forward when the butterfly came into their vision again but moments later they glanced down into the opening at their feet. A blanket of yellow was at the bottom, sparking their curiosity. The young determination reached forward to try to grab onto the butterfly that moved backwards out of their grasp before the child took a few steps back then ran forward, jumping after the small insect. Their hands closed around it, unknowingly the child ruined its ability to fly, as they began to fall towards the yellow blanket.
Once they landed Frisk realized that the yellow blanket was in fact soft flowers that broke their fall. In their hands they still held the butterfly and they looked at it closely, admiring the beautiful wings before noticing a small tear. It would no longer be able to fly… but on the bright side Frisk has a new pet! They plopped the disabled butterfly onto their tiny shoulders and examined their surroundings. They noticed an entryway with tall white poles surrounded by more flowers. Frisk stood up slowly and made their way to the rest of the mountain. They came upon another room and a soft, bouncy music began to play. In the new room was a single spotlight, which was showcasing a small, yellow flower. However, this flower was bigger than the others that Frisk had encountered, and it seemed to even have a face. How odd.
"Howdy! I'm Flowey, Flowey the- Hey! What are you doing?"
Frisk gave a cheesy little grin as they reached over to the flower that was now right in front of them. They plucked Flowey out of the ground and started playing with the petals. Flowey scrambled to get out of their grasp, but they wouldn't budge. Toriel hears Flowey screaming profanities and rushes over, preparing to help the small child from the demented plant, but stopped short. Apparently the roles were quite reversed and she looked very confused.
"Child..? What is going on here?"
"THIS DEMON GIRL IS-"
Frisk grabs a petal threateningly, "I no giwl! I detewmination!"
"You're not what, you insane candy cane?" Flowey the flower was not a happy camper. Toriel… was a very confused goat who is about to intervene when Frisk, the apparent determination, got up and ran over to her, carrying Flowey in their hand and a butterfly on their shoulder.
"He-Hello young one… what is your name?"
Frisk grinned proudly up at her, deciding instantly that they like the goat and will forever call them their goat mom. "Fwisk! And this is Buttew! He no able to fly so he no a buttewfly."
~~~~~~~~~~~~~~~~~~~~~~~~Time Skip!~~~~~~~~~~~~~~~~~~~~~~~~
After having Frisk walk down the hall without her, Toriel finally managed to get Flowey away from the self-proclaimed determination and set him on the ground. For once she took pity on the flower being held captive by the striped shirt child and so she freed him, watching as he disappeared into the ground.
"Now… Frisk, I apologize for this but I must go get something ready back at my home. Stay here, young one and I will be back soon. Here is a cell phone that you may use." Toriel handed Frisk the old, ancient cell phone and left after getting an 'okay goat mommy'.
After a few minutes alone Frisk decided to call Toriel and try to flirt with her yet the cuteness of them not being able to pronounce any 'r's caused an 'awww' and laughter from the goat-like monster. Eventually, Frisk got restless and went to explore the ruins. Along the way, they were approached by Froggit, who they decided would be fun to play with.
The two decided to play-fight, neither imaging how wrong it could go. Butter was set on the ground to watch them and be the referee of the play-match. Frisk was playing with their 'sword'(stick) and Froggit with his own usual attacks, but more carefully as to not hit the child, when Frisk tripped and hit Froggit with their full strength, causing actual damage to the monster. Frisk and Butter watched in horror as Froggit frowned and began to turn to dust.
Unknown to them, there was a spirit watching them closely. A young girl by the name of Chara who was waiting for Frisk to kill a monster. That time was now and it left an opening for her to take them over.
"Ah, much better. Having an actual body now makes it much easier to kill them all myself rather than have that stupid flower do it for me."
She picks up Butter and sets him on her shoulder, grinning wickedly. Frisk was currently stuck inside their own mind; forced to watch all the terrible deeds that Chara will do.