Sans will fight Chara and extract Chara from Frisk's soul.
Meanwhile, I will help Sans by 1. keeping my phone with me just in case anything goes wrong, 2. giving him DT before the battle, 3. keeping an eye on Chara, and 4. putting up defenses for the door to the throne room (just in case)!
To pass by the few hours, we decide that Sans will exhaust his energy if he practices. So, I give him DT. He checks his stats.
We managed to hack the way that Chara checks monsters' stats. Instead of his true stats of 9,999,999 hp, 25 attack, and 25 defense, we hacked it so it's now 1 of everything.
It's really awkward. Both of us have a sense of impending doom.
Then, we hear a pitter-patter of footsteps running rapidly to the beautiful corridor.
"hey, it's ok, tristy. you've got this. i've got this. we've nailed it in training, so why shouldn't we nail it now?"
"I know… I'm just worried, that's all."
"i am too." He gives me a big squeeze of an embrace, the type that only big brothers can give.
I smile. But at the same time, I'm releasing tears. I'm worried."Trying to squeeze my anxiety out?"
"you better believe it. tristy, I lo-"
But then the pitter-patter rushes towards us, and we scramble to our places.
Sans composed a monologue for the battle. Chara runs into the corridor… and stops.
"heya. you've been busy, huh?" The monologue starts.
Sans warns Frisk not to take another step forward, which Frisk does.
"welp. sorry, old lady. this is why i never make promises… you dirty brother killer!"
The battle begins.
"it's a beautiful day outside. birds are chirping, flowers are blooming. on days like this, kids like you…"
His eyes go completely black.
"should be BURNING IN HELL!"
He begins his attacks. Frisk is caught completely off guard as bones rapidly scatter across the ground and air. Frisk does various flips and leaps to evade them, but even then, Frisks gets hit a few times. And Sans hasn't even brought out the Gaster Blasters or telekinesis.
"hmm. i've wondered why people never use their strongest attack first."
. He keeps on attacking. Frisk tries to hit Sans, but misses. Frisk eats Papyrus' spaghetti to get more hp, but eventually, Frisk runs out and collapses to the ground.
Sans and I try to get ahold of Frisk's SOUL. Sans uses his powers to try and extract Chara from Frisk's SOUL, but…
It's not there.
"Sans, what happened? Why isn't Chara there?!"
"i don't know, tristy!"
Then, a wave of horror crosses Sans' face.
And I realize why.
Chara isn't in the SOUL.
She's somewhere else!
I hold Sans' hand, and he immediately grabs hold of me in an embrace and begins to cry. Not immediately. He doesn't do anything for a few seconds, until his body shakes in sobs.
And I know why.
Chara is never, ever going to stop until she kills my brother.

Frisk's body fades away, and slowly materializes at the nearby SAVE point. The SOUL floats to it.
And Chara almost sees me. Oh gosh, she almost sees me. We cannot finish this battle until Sans dies. We cannot.
Because this is just a game.
And we are just obstacles.

Hey Ella, a terrible tragedy has just occured. My mom. Took away. my. Blue. HOODIEEEEE
We go back to our places.
Asriel lied to me! Why? Why would he lie to me?
For 18 hours straight, Sans fights with Chara, full blown, all powers, just to live for the next fight. Then, sweat starts to bead on his forehead and he starts to get tired.
Finally, Sans makes a move which is different from anything else.
He says, "welp. here goes nothing. yep, it's literally nothing. and it's not going to BE anything either. ever. one of these turns, you're just gonna kill me. so, it's not going to be your turn. it's just gonna be my turn. forever. even if we have to stand here until the end of time. so, honestly, the most "determined" thing you can do here? do literally anything else."
Then, he pretends to go to sleep. I know he's pretending because one, he always lies down when he sleeps, obviously, and two, he snores literally every time that he sleeps. He's just standing there, his eyes almost closed.
Frisk is confused. Very, very confused. But then, a smile forms on his face.
But not a "happy" smile.
It's a "psycho" smile.
I can see the knife behind Frisk's back, and then she swings it at Sans. Miss.
Sans opens his eyes.
"heh, didja really think you'd be able to-"
What happens next is absolutely horrifying!
Frisk turns into Chara. I mean, TURNS INTO CHARA! The color of Frisk's shirt and the way that Frisk's face looks changes. Frisk's eyes turn crimson red.
Sans' eyes dilate in terror, and so do mine. His mouth opens, as if to scream, but no sound comes out.
In a move that can only be described as superhuman…
Chara takes the knife again and whips it from Sans' right shoulder joint all the way to his left hip bone.
Chara smiles.
I nearly scream.
Sans is shocked. All of his attacks stop. He clutches his chest. He falls to his knees.
Chara stands triumphant, the horrible smile still on her horrible face.
"dirty… little...cheater…" Sans says in pain.
He shakily stands up and limps slowly towards me.
Chara attempts to get towards the door, but she cannot. She screams in frustration as she bangs on the metal boards that we attached to the door a few hours ago.
Meanwhile, I catch Sans as he finally collapses.
"tristy… i… i'm sorry…"
"but… you have to… to... take in my powers…"
I nod, and tearfully I take a nearby candle. I extinguish it, toss out the wax, and, tears spilling down now, drop the heavy candlestick onto my right pointer finger.
CRUNCH!
It hurts so badly now, and I scream. I don't care, because Chara's screaming as well, and my screams mingle well with hers.
Sans touches my finger with his finger. Immediately, a blue and yellow light drains from his bones and goes into mine. For a second, I can see my entire skeleton now. It glows blue before it fades.
"Sans… oh, my gosh…" I stare at the wound from his right shoulder to his left hip.
"It's okay, buddy, just hold on, OK? Tell me you'll hold on. You've gotta hold on…"
Without a second thought, I latch onto Sans' hand and teleport to Alphys' lab/ hospital.
I just close my eyes, letting the tears fall without a fleeting thought of ever stopping them.
I grasp Sans' hand.
I open my eyes. A shudder runs through Sans.
"Please, hang on. Help is coming, you hear that? Alphys… she's coming. She's the Royal Doctor, she'll fix you up really good…. I can't… I can't lose you…"
I hear Alphys' voice.
"tRiSty, I HEARD THAt YOU- SANS!"
She gets a stretcher. I gently pick Sans up and put him in the stretcher, though it's not an easy task for both of us. Whenever I inevitably touch his wound, he reacts as if my hands are white-hot irons, and though he tries to hide it, I can see the tears slowly streaming down his cheeks.
Alphys tries to leave, but I stop her.
"Please…." I say, my voice breaking and my heart pounding. "Take real, real good care of my brother, ok? It might be his last moments… he's in so much pain…. and…. please. Promise me."
"I…." Alphys says.
"A-ALRIGHT. I PROMISE."
Sans is wheeled off to the makeshift hospital, and I position myself against a nearby wall. There's nothing else that I can or want to do.
I slide down it, slowly. I put my knees up and bury my head and hands into them. The tears still won't stop.
Delilah comes.
"Hey Tristana? Just wanted to make sure you were- uh… you're crying? Why? Didn't you win the battle?"
I just shake my head.
But then, I let it all out.
"No, I'm not alright! My brother is dying, and… I mean, I should've warned him…. I should've warned him…. and… and… I just wish that Chara hadn't come down here… I wish…. I wish…. I…."
I break. Tears stream down my eyes. Del stares at the sobbing mess that's me, and hugs it.
"Hey, I understand, Tristy. I really do. My dad's in there. He fell and broke his leg, so he's getting some rest. Maybe if the best happens, they can be bunkmates!"
"Honestly, Del… if I had one wish, that would be it."