(before i begin i'm going to point out some things, in this AU Frisk is 14 and she has only ever done pacifist route's and has also gotten Flowey to be on her side also Papyrus has started remembering more and more about past timelines, btw if the story is missing bits and pieces let me know and i will fix it because that has happened in the past)
Frisk woke up in the flower patch like she always did but this time was different she couldn't hear Flowey rambling on to himself. She got up and peeked around the corner only to find Flowey looking down not saying a word, Frisk ran up to him asking "are you ok ?" Flowey replied "i made a big mistake frisk… ill tell you on the way, right now we need to get to smiley trash bag".
Frisk was confused at first but grabbed a near by pot plant dug flower out and put him in it running for snowdin "what about mom ?" Frisk asked curiously. Flowey replied "I told him not to hurt her" Frisk looked at Flowey confused as she entered Toriel's house "who is he". Flower sighed and looked down as Toriel walked in "ah you must be friends of the other human my name is Toriel" Frisk's eyes widen'd and looked at Flowey "there is another human !?" Flowey glared at Frisk "like i said we need to hurry" Frisk nodded and bolted for the ruins exited and Toriel tried to chase after her but it was no use so she just went back inside. "Are you going to tell me about this human or what" Frisk asked excitedly.
Flowey replied "remember how i told you about the last human who came here" Frisk replied "the ballerina killed by Undyne ?" "yeah that one". Flowey shivered "her older brother is here and his out for blood… he would give Chara nightmares. Frisk's eyes widened but she wasn't paying attention to were she was going and ran right into sans knocking them both over "Sans got up and helped Frisk up "heya kiddo whats the hurry did Toriel get your goat" Frisk just looked at Sans worried and he suddenly knew this was serious "kid whats going on thats your serious face"
Flowey explained to Sans and Frisk that he had told the human about what Undyne did. Sans spoke up "what does he look like" Flowey replied "he wore a mask with a skull painted on it and wore black clothing… his eyes were empty and dark like he wasn't even there and his soul was black and dripping ooze" Frisk shivered at the thought "we need to get to waterfall" Sans smiled and replied "i have a shortcut"
Sans grabbed Frisk who was still holding Flowey and they were teleported to waterfall and started walking until Sans broke the silence looking off in the distance "is that Papyrus what is he doing out here ?" Sans teleported the group to him once again to Papyrus who jumped back at the sudden appearance "Sans ! you know it scares me when you teleport to me…" he suddenly looked at Frisk and Flowey "human ! Flowey ! "he picks up all three of them hugging them "i met another human and he as very polite and said he would try my spaghetti" Sans smiled "thats great paps but your new friend is trying to kill Undyne" Papyrus gasped dropping them and staring at Sans in disbelief. Frisk ad Fowey both said "its true and we need to find him" Papyrus looked back the way he came "i showed him Undyne's house"
Sans grabbed Papyrus and Frisk as fast as possible teleporting them to Undyne's house looking in the window that Papyrus usually jumps out of to see the human kick Undyne's door open making Undyne bolt up grading her spear "who the hell are you ?!" the human stared at Undyne for a moment then spoke up "are you Undyne the undying ?" Undyne raised a brow and looked at the human curiously "yes, and who are you". The human chuckled "i am so glad you asked, i'm the brother of an innocent little girl you killed" Undyne dropped her spear and looked at him in disbelief "how do you know about that" The human replied "a flower told me".
Flowey looked down but no one noticed as they were waiting to see if he would attack or not "he told me she was dancing with someone named Shyren when you drove your spear through her stomach" Undyne teared up looking away which made the human looked at her confused then seemed to grin "you're filled with guilt because of it aren't you, well that wont change anything because im going to do the same to you" he suddenly pulled out a black machete and Papyrus breaks through the window screaming "dont kill Undyne she is sorry". the human's eyes widened suddenly and backed up as Sans and Frisk came in and Papyrus spoke up "you will have to get past i the great Papyrus my brother Sans and the human to get to Un-" the human suddenly cut Papyrus's head off and rushed to sans who teleported out of the way. The human continued to slash at Sans who would dodge and launch bones at him until they exited Undyne's house where Sans launched a Gaster blaster at him but he dodged pulling out a second machete looking at Sans who was now standing beside Undyne.
They nodded at each other and charged the human. Undyne launched spears at him while Sans summoned bones at him. The human blocked the attacks with his machetes slashing at them both cutting Undyne's face and tearing through Sans' hoodie.
Frisk and Flowey were inside just staring at Papyrus's head that had somehow not turned to dust, suddenly a bone flew past Frisk who snapped back into reality setting flowey down running outside and up to the fight "stop it" screamed the now crying Frisk. This caused undyne to stare at Frisk when suddenly a machete hit Undyne in the stomach and she gasped throwing a spear into the humans shoulder who served in pain as he lashed at Sans slamming his machete through a faster blasters head tackling Sans out of the air and swings at Sans who uses his blue attack to launch the human into a nearby rock wall.
The human got up laughing "i thought i was the only one with those kind of powers" suddenly black smoke starts coming out of the eye holes of the humans mask and he launches a ball of black liquid at Sans who dodges it but is then immediately struck by the machete and pushed to the side slowly turning to dust. The human turned to Frisk and said "fight or run away" Frisk then thought of when Toriel said the same thing to her and spoke up "why did you have to do this why couldn't you have just talked it out… Frisk looked down at the pile of dust that was beside her that used to be Undyne. The human then gasped as a bone went through his chest as sans coughed up blood. "Sans get into the ruins after the reset !" the human looked at Frisk with confusion before falling to the ground turning into a puddle of black ooze.
Frisk then reset waking up in the flower patch bolting through the ruins completely forgetting about Flowey, she ran through Toriel's house jumping down the stairs and ran into Sans who helped her up. He's at the end of the ruins we will cut him off at Papyrus's first gate. Sans teleported them to the gate where they saw the human approaching who didn't seem to recognize them Frisk whispered to Sans "lets keep it calm and try to talk him out of it" Sans nodded and waiting for the human who greeted them "hello there i am wondering if you know what happened to a girl in a tutu that came down here 10 years ago. Sans nodded "yeah i know but lets talk about this at grillby's and keep your cool" the human sighed knowing what might be told to him soon.
(that is the end of chapter one, if you have any comments please be honest and also i just want to let you know that i don't write stories that much so it might not be that good so if you have any pointers please let me know)