"What do you mean by that, pal?" They spat.
"You know what I mean."
"I want to hear you say it."
"Fine. I'm going to take over your body! I'm going to do what I have to! Happy?"
"No, actually, I'm quite furious, that after all we've been through you still can't see that there's always a way!"
"And I can't believe that someone could be so stupid like you are! You can't win them all Frisk! You can't always get what you want! We have to survive, to keep moving, and I'm going to get us there, like it or not!"
Undyne had kept talking, oblivious to the internal struggle below them. Suddenly, she erupted, catching the attention of both children.
"SCREW IT! WHY SHOULD I TELL YOU THAT WHEN YOU'RE ABOUT TO DIE!?"
She looked to the sky and yelled, shattering her helmet with the force of it.
"YOU! You're standing in the way of everyone's hopes and dreams! Alphys' history books made me think humans were cool, with giant robots and flowery swordswomen!"
"Wait what?"
"Focus, Frisk!"
"But you? You're just a coward!"
The implications did not need to be spoken, Frisk already knew what Chara was thinking, loud and clear.
"Hiding behind that kid to save yourself! And your pathetic goody-two-shoes-schtick! Oooh, I'm making such a difference by hugging random strangers!" She mocked.
"You know what would be more valuable to everyone? IF YOU WERE DEAD!"
"Frisk, she-"
"SHUT UP, CHARA!" Both stopped as Frisk yelled aloud. It was quite possibly the loudest they'd been since their fall into the Underground, and certainly the most passionate. Undyne looked confused for a second, then continued.
"T-that's right human! Your continued existence is a crime! Your life is all that stands between us and our freedom! Right now, all our hearts beat as one, everyone's waited their whole lives for this fight, and I will win it, for all of us! Now prepare yourself, Human! Let's end this. No more hiding, no more running! I will show you how determined monsters can be!"
As she slid down to meet them, Chara dared not ask, but Frisk chose to speak.
"We're not going to die here, Chara. I won't let us. We must keep our soul. We have to go on. We have to win. But I will NOT kill. And neither will you."
The spirit had fallen silent, evidently not willing to challenge them at the moment.
Undyne prepared to attack, and legions of energy spears appeared around Frisk. Frisk knew they couldn't dodge them all. After a moment of panic, their soul, usually red, flickered, before becoming green.
"Chara, what is-"
"I don't know, but look!" The heart projected a green shield, not dissimilar to Undyne's spears.
"It's like Papyrus earlier! The soul has, changed, somehow?"
"No time to think, incoming!"
Chara was right, the spears began to move, in barrages as Undyne continuously summoned more. Frisk realized that the best way to defend themself in this battle was to face the challenge head on, just like she fought. Still, that didn't give a solution on how to get out of the predicament without bloodshed. Suddenly she stopped, evidently exhausted for the moment and the heart turned back to red. In that moment, Frisk saw an opportunity, as her words came back to them.
'No Running?' she had said. But was that really true?
Frisk decided to try and run past her while she took a second to rest, maybe running would be the thing to save them!
But Chara had other ideas. After Frisk managed to get past Undyne, they suddenly found themself wheeling back around, as their arm swung viciously, carrying the toy dagger they had picked up all the way back in the ruins. Frisk didn't even feel themself reach for it. Of course that was because they didn't; Chara did. Just as Chara had chosen to literally backstab Undyne.
"Chara!"
"It's the only way!"
"No it's not!"
They were interrupted when Undyne, recovered from the sudden injury turned to face them and delivered a fierce thrust into their sternum, resulting in a surge of pain that silenced the both of them.
"You truly are scum! Too weak to fight me head on! Pathetic! Now die!"
Once more the spears apparated, and the shield returned. However, Chara knew what they were capable of now. Knew that they no longer had to be a passenger in this journey. And Frisk was terrified. They screamed at their own body, trying to pull away desperately, as their friend hacked and slashed in between dodges and blocks.
Finally, Frisk had had enough. They accomplished what they never had to before, what they never wanted to try, and completely suppressed their other personality. Instead of focusing on pulling themselves back, trying to grab the reigns of the situation, they just pushed Chara out. They had locked them away. No muscle control, no words, hardly even felt. Chara resisted, of course, but Frisk maintained control. With much effort, Frisk was able to continue the original plan, and after some running noticed a sign, claiming they were entering a new area of the Underground: Hotland. Frisk kept running, easily noticing a sudden increase in heat. The environment had shifted from a dark marshland to a vast, open landscape, with lots of pillars of solid, red rocks, almost like those of a deep canyon. Endless lakes of lava could be seen far below, all the more reason to keep running. They were so focused on escaping, they had barely noticed Sans sleeping at a guard station until they had passed it, crossing a wooden bridge. Frisk began to notice that Undyne was slowing down.
"Armor…so…hot. But I… can't… give up!" She declared, before collapsing to the ground.
Frisk looked for a way to help, and saw a nearby water cooler, complete with standard styrofoam cups.
"Don't you dare." A familiar voice quietly welled up from inside, a snarling, hissing, whisper. Frisk was starting to slip.
"She's just doing her job. Do you remember what that flower said, long ago?"Chara did, but allowed Frisk to continue.
"They promised we would face an enemy that would not give up. An enemy that would stop at nothing. Someone who would kill us over and over, and that we would not be able to stop them without violence. That flower was wrong. Undyne was more dedicated and determined than any other monster we've ever seen, maybe more than any in the entire Underground. But we've beaten her. She's done. Now is the time to prove that we can rise above the violence that our people are known for. We can prove that humans can be compassionate, patient, everything we want to be. Now more than ever, is the time for mercy."
They moved towards the cooler, and Chara made no further objections, evidently mulling over their words.
Frisk carefully carried a cup to Undyne, and spilled it on her, trying to coat her evenly.
She immediately stood, looked down at the child, looked around, then turned, and slowly walked away without a word. Frisk realized how tense they were, and relaxed, allowing Chara to return.
"Well. You continue to impress."
"Yeah? Didn't sound so 'impressed,' when you tried to use my own body against me and abandon everything I stand for!" The words were dripping with venom, and Frisk was aware of how they must hurt. But they didn't care right now.
"Look, I just… I… I don't know." They sounded overwhelmed.
"Don't know what?" Frisk asked, voice softening as they became a bit more concerned.
"Don't know what's wrong with me! No matter how I try, I can't do it! I always come back to… this! I-i just, I have too much. Too much hurt, too much pain, too much hate. Memories that haunt me, mistakes I've made, and regrets I can't begin to count." They were beginning to cry, sobbing uncontrollably. Finally, they began to calm down after quite a while, as Frisk recovered their physical injuries. Frisk chose to stick with their usual policy, no questions. They had the feelings answers would come, sooner or later. Chara's focus shifted.
"How did you do that?"
"Do what?"
"The… the locking thing. Suppressing me, pushing me away?"
"Why, so you can do it to me?" Frisk stopped.
"I-i'm so sorry, I didn't-"
But it was too late. Chara had already blocked themself off. Once again, they put some distance between them. They had just opened themself up, more than ever before. Many emotions were raw for both personalities, all the more reason to build bridges instead of walls. Frisk had seen a sensitive side of Chara, and in their anger they had taken advantage of it to hurt their friend. Frisk had blurted it out so quick, and desperately wished they could take it back. But they couldn't. And just like the rest of the events that had transpired, it ensured that nothing would ever be the same again.