(Just so you all know, Italics is Frisk and bold is Chara)
(Also, spoilers if you have not completed the game and I am using what I think Frisk is. I like the idea that Frisk is a boy. I know they are neutral gender, but I though he was a boy at first. So please don't try to correct me on that, I know. If I do make a mistake, please tell me. These are just head canons pretty much. Anyway, continue on!)
The human just finished talking to Flowey. They are now on their way to meet Sans, to get judged for their actions. One part of them feels guilty, wants to put down the knife, go back and try again. To take back their actions. Another part of them wants to continue, kill the joking skeleton and destroy the world for what it is. An angel and a devil, wondering what to do with their life.
The truth is that there are two different souls in this human body. Yes, the body of a 8 year old has two different souls within him. One good, one bad. One girl, one boy. The boy was in control before he came to this world. The girl didn't start taking control of him until he made the choice to attack a dummy.
The girl, who goes by the name of Chara, tempted the boy to hurt people. She has succeed in taking more and more control over his body, up to the point where she just has to kill a few more people to gain full control over this body.
The boy, who goes by the name of Frisk, fell into temptation. And now, as they walk this path, he wants to go back. Memories of his past life come back, when he came down here. All these people were his friends, he made Flowey become good again. All was well. And now, he has to watch as he kills everyone he befriended.
"The time has come," said Chara. She smiles and grips the knife as she walks closer to where Sans, the punny skeleton, was waiting for them.
Please don't do it pleaded Frisk. He couldn't stand to watch Chara hurt another one of his friends.
"Just sit back and watch, boy. This is the path you have chosen for yourself." Frisk stayed silent, knowing she was telling the truth. If he hadn't attacked the dummy, Chara wouldn't be there.
The children stop in front of a smiling skeleton, staring at them with his hands in his pockets.
"Heya," he said. "You've been busy, huh?" He looked away, staying silent for a moment, before looking back at the human before him. "So, I've got a question for ya."
Does he know that you killed Papyrus?
Don't you mean when you killed Papyrus? Frisk stayed silent after that.
Sans closed is eyes before continuing to talk. "Do you think that even the worst person can change…? That everybody can be a good person, if they just try?" Chara walked forward( (remember, Chara is in control. Right now, Frisk can only watch)), closer to the skeleton. Sans just laughed.
"Alright," he said. "Well, here's a better question." Sans opened his eyes, and Frisk's eyes widened when he saw that his pupils weren't there any more. ((Frisk has his own soul like body, but has no control over his physical body. If you have seen FMA, then I am going off of Greed and the prince)).
"Do you wanna have a bad time?" He closed his eyes again. "Cause if you take another step forward…". He opened his eyes.
"You are REALLY not going to like what happens next."
Chara, just walk away now commanded Frisk. Chara chuckled.
Im not backing down from a fight. Chara took another step forward.
"Welp," said Sans, as Chara did this action. "Sorry, old lady. This is why I never make promises." The magical music that played when they enter a battle, except this was new, started playing as Sans stood there and continued talking. Eyes closed, hands in pockets.
"It's a beautiful day outside. Birds are singing, flowers are blooming. On days like this, kids like you…" His eyes snapped open and he gained a voice with more anger.
" l." He pulled out his hand and pushed Chara to the ground. He brought a bed of bones up, causing Chara to loose most of her health. Chara got back when he threw a wave of bones at her, which she dodged expertly. Gasters came out of nowhere, and Chara accidently burnt her hand on its beam. She avoided the next Gasters and glared at Sans as she was almost dead.
"Heh. I never understood why people never used their strongest attack first."
Chara, just give up. There is no way you can beat him. Chara got up, despite being almost dead, and grabbed the knife that she had dropped, charging at Sans. She held her knife out where his stomach would be and ran at full speed. Frisk watched in horror as she got closer and closer to Sans, then… she missed. Chara blinked and looked to the side in confusion, then anger when he saw the skeleton standing there.
"What?" he said with a shrug if his shoulders. "Did you really think I was going to stand there and take it?"
This went on for a few hours. Chara kept dying, Sans kept making witty remarks, it went on and on. Until it got to a certain point in the fight.
"You, uh, really like swinging that thing around, huh?" he asked. He stayed silent for a moment. "Listen. I know didn't answer me before, but… somewhere in there. I can feel it. There's a glimmer of a good person inside of you. The memory of someone who once wanted to do the right thing." Chara stared at him while Frisk listened closely to what he was saying.
"Someone who, in another time, might have been… a friend? C'mon, buddy. Do you remember me?"
Don't listen to him, Frisk. He is tricking us. But Frisk didn't listen to her. He listened to Sans as he continued talking.
"Please… if you're listening… let's forget all of this, okay? Just lay down your weapon, and… well, my job will be a lot easier." Frisk popped his head up and smiled. It took a while, but Frisk finally gained control over his body.
What are you doing?! yelled Chara.
"Fixing what you started," mumbled Frisk. He stood up, feeling heavy from the fight. He shivered as he felt Chara's sins crawling on his back. He dropped the knife and stumbled towards Sans, a happy and relieved smile on his face. Sans opened his arms and it seemed as if the smile on his face got brighter.
"You're sparing me? Finally. Buddy. Pal. I know how hard it must be… to make that choise. To go back on everything you've worked up to. I want you to know… I won't let it go to waste." He stayed silent as Frisk fell into his arms and started crying. Sans was surprised, but he smiled.
"I'm sorry… I'm sorry… I'm sorry, I loved him, I'm sorry.." sobbed Frisk.
"C'mere pal." Frisk hugged him tight. Then gasped as he felt himself be lifted into the air, then slammed on a bed of bones repeatedly. He laid on the ground, almost dead.
What are you doing?! Get up! He heard Chara yell at him from inside. But he didn't listen. Sans came over and leaned over the boys body.
"Geeetttttt dunked on!" Frisk slightly opened his eyes to see Sans. Despite everything that happened, he smiled.
"I understand Sans… I loved your brother in the other timeline… I don't blame you." He took a breath as a tear rolled down his cheek. "You're still my friend. I love you." Sans watched him, and sighed.
"If we're really friends… you won't come back." As he faded away, Frisk just nodded his head.
"She won't…" With that, Frisk faded away. Sans waited there, then sighed in relief when he saw that Frisk never came back.
"Guess the kid ran out of determination…" Sans chuckled, sat down on the ground where Frisk last was, and let tears stream down his face.
"Why am I crying?" he asked himself. He never got an answer. All that was left was him and King Asgore. There was nothing they could do. The monsters were completely wiped out. He looked up from the spot he was staring out to see white particles taking away the hall he was in. He chuckled when he realized what it was.
"Gee, kid. Can't leave it at that, huh?" Though he sat there, staring at the ground. Memories of past timelines came in his head and he let tears stream down his face. He remembered Frisk saying how he promised to protect everyone. Sans just chuckled.
"I guess you are keeping you're promise after all this time… Thanks kid." As the white particles of the true reset came along, Sans said his last few words.
"I'll meet you at Grillby's, kid… Do you want anything… . . . ? "