Addition : Turnabout's fair play

-FH-

A/N:

I began to write this under one plot bunny, but it switched to another after the RESET. I think the way the two mixed makes a pretty amazing story that might explain why a Pacifist could go Genocide, if you follow a few inferences.

-FH-

Undyne supervised Papyrus' tomato mashing as she gave her third weekly lesson in the skelebros' surface home. It was still hard for her to believe they'd all actually made it out!

From the next room, she caught snippets of Sans' side of a cell phone conversation.

"so why exactly did you go to see it, kiddo?

"no, that thing deserves the word it. do you know how many times-" He was cut off by whoever was on the other end.

Undyne blinked back to the lesson, ducking just in time to dodge a scrap of the tomato Papyrus had just crushed with his full bodyweight.

"look, fine, why did you go to see him?

"... that's a joke, right?

"kid, i don't know what you think you're planning, but trust me: s. t. o. p.

"this is the happy ending. everybody is alive. everybody is out. don't-

"reliving the same events is awful for your mental health. why do you think it- er… he, turned into what you met when you fell?"

Papyrus was staring at her. Undyne looked up, realizing he was talking. "... HAVE DEFEATED THESE TOMATOES, UNDYNE!"

"Right! Yeah! Start with the noodles. MAXIMUM temperature!" Undyne sent Papyrus on his way to putting pots and starch on the stove, wandering over to the archway to eavesdrop on Sans' conversation.

"kiddo, please don't. come on, you have everything up here. friends, laughs… unpredictability. there's no reason-" Sans halted mid sentence, looking at his phone. The call had disconnected.

Undyne watched as he shot up from the couch.

"hey, paps, undyne, i gotta run. thing just came up at the mountain." Undyne thought she could see sweat beading on Sans' brow. Weird. Skeletons couldn't sweat, right?

"BROTHER, DOES THIS THING REQUIRE THE ASSISTANCE OF THE GREAT PAPYRUS?"

"nah, bro, i think i got this." Sans opened the door, stepping out.

Undyne followed, but found the street outside the house empty. Sans had already done his weird vanis-

RESET

Undyne paused in her early morning training run. An image of a pink striped sweater, a face as well, flashed through her mind. Then it was gone.

She shook her head and kept running through the dark canyons of Waterfall. It must have been some scene from an anime that she'd half remembered. Undyne noted to herself to watch whatever it was again with Alphys.

-FH-

"B- But-" Alphys stammered, her voice even more tinny and halting over the cell phone call.

"No buts, Alphys! If this thing gets to Hotlands-"

"B- But it w- won't! Y- You'll stop it, r- right?! A- And you'll come back!"

Undyne grimaced, holding the phone in a crushing grip. "Yeah. I'll stop it."

"T- Then-"

"But if I don't, you have to promise me you'll evacuate everyone. Somewhere the human can't get. And call Asgore!"

"U- Undyne-"

"I need you to prom-" Looking up, Undyne spotted the human walking out on to the bridge. Then, right on their heels… "Damnit! That kid!"

"W- Wait, UNDYn…"

Undyne dropped the phone, leaping off the ridge near the bridge's end. She landed just in time to stand herself between the Monster Kid and the human.

… Between the Torn Notebook and its target.

"Ungh!"

For an instant, the scene was motionless. The dust settled, scattering out of the gash cleaving Undyne's armor from shoulder to waist. Then the child broke the silence. "Undyne… You're… You're hurt…"

The Monster Kid was behind Undyne. Struggling to stand tall, she flashed a grin over her shoulder. "Hurt? It's nothing," she lied. "Next time, listen when I tell you to leave, okay?"

MK whimpered, curling up a little.

"I'll take care of this! Get out of here!" Undyne snapped, glaring at the hu… no… the THING.

Footsteps retreated behind Undyne as she finally got a good look at…

"... What…? You…?"

The half memories of the anime resurfaced, the human in the pink and purple befriending dozens of monsters. A warm glow came with it, something that felt like… friendship?

"You would… kill… a kid?" Undyne coughed, her hand going to her torso. It came away with a healthy coating of dust. "And now… s- somehow, with just one hit…"

Undyne looked up into the emotionless face, but the image before her eyes wouldn't sit still. It blurred and warped, replaced with an image from her own mind's eye of the same child clean of dust, crying on the ground. She blinked, finding tears welling in her own eye.

"W- Why… why are you…" Undyne trailed off, feeling her time running out.

Distantly she heard the rush of water in the river below. Something else was there too: tinny sobbing, from over the cell phone she'd never hung up, and now never would. Alphys was on the other end. Alphys was watching. Alphys was crying.

"No…" Undyne refused. The strength she'd seen in the human from those half memories, it was the same strength as in this human! But something was wrong, really wrong, with this human!

Undyne was DETERMINED to fix it.

"You don't feel anything when you kill people, do you?"

The human's face betrayed nothing.

"Killing you wouldn't solve anything, would it?" The human cocked their head. Undyne grinned, standing up. Something, deep down in her SOUL, just wouldn't let her die! "No, you're not afraid of death at all, are you?"

Feeling life flowing back into her, Undyne laughed.

"Fuhuhu! You think you can escape consequences? That even guilt can't touch you?!"

She summoned a blue spear, then tossed it aside.

"I'll give you the worst punishment I can devise, then!" Undyne shouted, feeling the burning reaching a peak within her SOUL.

Light began to fill the canyon. It took a moment for Undyne to realize it came from herself, but by then it had become blinding. For a moment, she closed her eye.

When she opened it, she felt taller, stronger… whole. "I'll give you… MERCY!"

Undyne did nothing, waiting for the human's response. Somehow she knew the human in her memory and this one were connected. If she could just get the human to remember-

Undyne saw the Torn Notebook sweeping out at her. She did her best to dodge, stumbling backward, but she tripped over her armor. She fell hard onto her rear end, trapped in the middle of the bridge. Against the human's next blow, she was defenseless.

The blow was merciless. The left side of her head and her left arm were cleaved off in an instant, both immediately beginning to turn to dust.

"I don't… know what I was thinking…" Undyne sagged. "Why would… I have ever… been friends… with…"

She felt hersel . . .

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...

Footsteps retreated behind Undyne as she finally got a good look at…

"... What…? You…?"

She narrowed her eye. The sweater… the face… This human wasn't supposed to be violent! Something was broken and she had to fix it!

"I'll give you the punishment you deserve!"

Light filled the canyon. When she opened her eye, she felt taller, stronger… whole.

"I'll give you… MERCY!"

The human flinched, beginning to shake and sweat. Undyne stood still, unwilling to accept failure of her terrible plan.

The Torn Notebook steadied, the tremors in the human easing out from there. Then, suddenly, the human struck. Undyne didn't have time to react before the notebook cut into her, practically slicing her in half.

"I don't… know what I was thinking…" Undyne sagged. "Why would you ever change your ways? You didn't for Papyrus…"

She felt hersel . . .

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"... MERCY!"

The blow was immediate and devastating, leaving no time at all before Undyne bega . . .

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Footsteps retreated behind Undyne as she finally got a good look at… whatever it was. The THING glared back, looking incredibly annoyed with something.

"... What…? You…?"

The human nodded enthusiastically, running forward to Undy-

The blow came from outside Undyne's vision, entirely blindsiding her. Undyne's head and shoulder slid to the ground as the gash across her chest doubled in depth. The rest of her body dissolved.

For some strange reason, the human looked shocked.

"Not even honorable… enough for battle. I… see… how… it…"

Undyn . . .

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"... What…?"

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"...You…?"

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"... Would…"

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"... Kill…"

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"... a…"

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"... kid…?"

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"W- Wait, UNDYn…"

Undyne dropped the phone, leaping off the ridge near the bridge's end. She landed just in time to stand herself between the Monster Kid and the human.

… But the human ducked past her.

"NO!"

The kid gaped as-

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…

"I need you to prom-" Looking up, Undyne spotted the human walking out on to the bridge. Then, right on their heels… "Damnit! That kid!"

"W- Wait, UNDYn…"

Undyne dropped the phone, leaping off the ridge near the bridge's end. She landed just in time to stand herself between the Monster Kid and the human.

… The Torn Notebook came down, gripped in two of the human's hands.

The flat side of the notebook smacked the human's knee hard, bending and then breaking. Unable to hold the whiplash, the two pieces snapped out of their grasp and tumbled off either side of the bridge.

Before Undyne knew what was happening, the human threw their arms around her, sobbing. The fish monster warrior flashed back to half memories of a pink and purple sweater, another crying face…

"What…? You…?"

She glanced over her shoulder. MK was grinning like the idiot he was. "S- See Undyne? Yo, I was… totally right! No way this human hurt anybody! Yo, it must be some sorta misunderstanding!"

Undyne shivered as the mass murderer held her leg tighter, sobbing all the harder. A warm feeling was bubbling up inside her, but it made her queasy. How could this human have ever been her… friend?

Suddenly, Sans. The skeleton walked out from behind MK, who immediately freaked out at having been hiding someone without realizing it.

"hey, i just happened to be passing through when i saw this little party."

"S- SANS!" Undyne shouted, startled, "What are you doing-"

"i happen to be on my way to grillby's. was wondering if this dirty brother killer wanted to come along."

The human sobbed, sinking to their knees but remaining wrapped around Undyne's leg. Their hands began to blur, forming symbols faster than Undyne could see, even if she could get a good look.

"it doesn't matter what she said. just think about it logically: why would killing anyone solve asriel's problem?"

The human began signing more symbols to Sans. Undyne grit her teeth and crossed her arms, waiting for the awkward situation to end.

"look: asriel's gone. flowey's all that's left and he won't be changing any time soon. accept that. let's just forget all this happened and go back to the good times."

The human whimpered, but nodded.

Undyne's patience ran out. "Forget WHAT happened, Sans?! People are DEAD now! We can't seriously be consideri-"

RESET

"Oooh! I'm making such a difference by hugging random strangers!" Undyne mimicked, then spat. "You know what would be more valuable to everyone? IF YOU WERE DEAD!"

The human deflated a little, taking deep breaths. The Stick in their hand sagged a little.

This was the middle of her speech and the human was TAKING A BREATHER?! Not on Undyne's watch! "Now human! Let's end this, right here, right now. I'll show you how determined monsters can be! Step forward when you're ready! Fuhuhuhu!"

The human took a step forward, the Bandage barely adhered to their face bouncing. They tightened their grip on their Stick.

"That's it, then!" Undyne jumped off the cliff, spear-first. "HERE I COME!"

Undyne hit the ground. Not a moment later, arms wrapped around her leg. The human had dropped their Stick, and was hugging her!

"HEY! What did I JUST SAY about hugging!"

Undyne gave the human a shove, trying to extricate her leg. The little person wouldn't budge.

"Now you're really making me ANGRY!" Undyne shouted. The human gave no sign of hearing, just hugged tighter.

Snarling in annoyance, Undyne lifted her leg - human and all - off the ground and gave it a few kicks. Somehow the human managed to stay attached.

"NGAAAAH! IF THIS IS HOW YOU WANT TO DIE, SO BE IT!" Undyne summoned a spear, raising it over her head and aiming to stab right down, parallel to her own leg.

… She paused, staring at the defenseless kid. They were tiny, had a striped shirt, and not a speck of dust on them. A question drifted into her mind, in her voice. Probably her conscience, or something. "You would… kill… a kid?"

Undyne smashed her spear on the ground. "WHY ARE YOU SO CLINGY?!"

The human looked up at Undyne. The fish warrior realized, then, that they'd been crying a lot. Fresh tears, from just now, slowly rolled down their face too.

"Stupid brat," Undyne muttered. The human hugged tighter, hiding their face in her armored leg. "I'm gonna KILL you later, you hear me?"

The human didn't respond.

Undyne took an awkward step with the human still attached. "You and me, we're going to my place for now, until you get OFF OF ME."

The human held on tighter.

"But THEN I'm gonna kill you! In a FAIR FIGHT!"

She felt the human shrug.

She set off back toward the bridge. "C'mon. My place is AWESOME! It's shaped like a big fish and…" Undyne trailed off, realizing she was using the babbling she needed to fill space when Alphys was feeling down. "... right. It's cool."

Undyne took about fifteen steps before the weight was too much for her.

"Damnit kid, GET OFF or I'm going to KILL YOU!"

The human let go of her leg, standing slightly away and looking alone.

"... I'm still gonna kill you," Undyne vowed, though her SOUL wasn't it.

The two of them began to walk quietly back through Waterfall.

"... Damnit Papyrus," Undyne muttered, "I knew you'd rub off on me. Stupid skeleton with your stupid pacifism."

-FH-

A/N:

Alright! So, our Pacifist!Frisk ended up chatting with Chara, who told them that a Genocide route might help them SAVE Asriel for real. Because they were visiting Flowey, he was the only person they had to talk to about it.

So they RESET.

Then this happens.

I hope you enjoyed!