Frisk was heading down to Snowdin town. Sans, the most powerful Monster they'd ever met, was down first. They couldn't have ever imagined an easier time for them. All they have to do now to be totally safe is kill Undyne, and then they're free to kill all without anything painful coming to them.
"Papyrus!" Frisk called out to the tall skeleton, acting as if they were almost in tears. "I can't find Sans!"
Papyrus looked worried. "He's normally out there..."
"I... I f-found some dust, Papyrus!!" Frisk exclaimed, which immediately changed Papyrus's expression to a look of shock that Frisk had never seen on anyone's face before.
"You... you what??" Papyrus grabbed Frisk by the shoulders.
"He... h-he's probably dead..." Frisk cried.
Papyrus paused for a moment, not sure what to say, then hugged Frisk tightly, and began to cry.
Frisk wiped their tears.
"... Didn't know I could make myself act so well." They said out loud, causing Papyrus to return to his look of shock, as Frisk raised their knife.
Laughing uncontrollably, Frisk walked down Waterfall, about halfway through it. They didn't care that they were making noise. They didn't care that Undyne would find them.
It was just too funny~
Papyrus was the easiest person to trick, wasn't he? Just fake-cry a little and he's on your side. Maybe just say 'I'm sorry' when you're a genocidal murderer, and he forgives you. Or, even better, you don't even need to say anything~
Ahh, so many ways that he's stupid... and adorable.
"HUMAN!!" The voice of the familiar Captain of the Royal Guard boomed out from behind them.
"I knew you'd show up eventually~" Frisk chuckled, trying to suppress more uncontrollable laughter. "So, do you really think you can beat me?"
"I don't think, human." Undyne smirked. "I know."
"Try me!" Frisk challenged, whipping around to face their opponent.
Undyne summoned a spear in her hand. "Of course I will."
Frisk hadn't expected this. Undyne was a lot stronger than normal, and of course, they'd only killed 2 people... only gained 1 LV.
Plus, Undyne appeared to get stronger with a stronger purpose. And that wasn't good. Not at all.
"What's the matter, human??" Undyne roared. "Can't beat me?!"
Frisk growled. "Of course I can!!" Releasing in their strength all the energy and rage built up inside them, they threw their knife at Undyne, missing her chest but piercing into her arm, leaving a break in her armor as well.
Undyne pulled the knife out immediately. "You can't just throw some silly knife at me and expect me to die, human!!" She declared loudly. "Give up!"
Frisk laughed in reply. "Give up? Since when do I EVER give up?"
But as the battle continued, Frisk got tired. Undyne seemed to have unlimited energy, and Frisk used a lot on throwing that... that darn STUPID knife that couldn't even hit it's target.
Eventually, when Frisk had gotten tired enough, Undyne took her chance and ran up to them, hitting them in the head, knocking them unconscious.
They woke up in prison.
Undyne was standing outside their cell, staring angrily at them.
"You've made quite a name for yourself just by killing one person, you know."
Frisk paused, then started laughing. "ONE person? HA!"
Undyne made a confused look. She thought she'd have heard about it if someone else died... right?
"Who?" She demanded.
Frisk's smile disappeared for a moment, then returned as a grin. "Papyrus."
Undyne summoned a spear and immediately threw it aimed at Frisk's head, and Frisk dodged barely, feeling it scar them.
"You did not!!" Undyne roared.
"I did." Frisk changed their smile again, giving Undyne a sweet, innocent look.
Undyne growled, then stomped away, burning with anger.
A couple seconds after she exited the Dungeon, Frisk heard a scream, then the familiar sound of a body turning to dust.
Instantly, Frisk picked up their knife and got ready to fight.
"Who's there?!" They demanded, but nobody came.
Then, a whisper.
It sounded familiar... yet it didn't. Frisk didn't know what to think, it was too quiet.
"... I made my decision..."
"... W-What decision?!" Frisk exclaimed so loudly they were surprised at themself.
They heard chuckling, then another quiet answer, probably deliberately quiet to conceal the person's identity.
"Search your memory, you idiot. Don't you remember the deal you tried to make..?"
"What deal?!" Frisk screamed loudly in spite of themself.
But there was no answer anymore.