Ruby, Weiss, Blake, Yang, Zenitsu, and Inosuke cornered Daki on the roof of the building. 

Daki: Damn you! 

Zenitsu: Before you die, I ask that you apologize to the girl whose ear you nearly tore off. It may be your money that pays for their clothing, food, and housing. But they are not toys! 

Ruby: Yes! They're people who have feelings, and the fact that you would use them like that is deplorable! 

Daki: Oh spare me the lecture. What makes you think ugly freaks like you can talk to me like an equal. Here in the Entertainment District, women are always being bought and sold. Their owners can sell them, buy them, or break them. Those who provide no value don't deserve to be treated like human beings. 

Blake: You must have been mistreated too in the past when you were human. But you should know that it's wrong! 

Daki: The sufferings of my past were lessons on what to do to others as revenge! If I don't cause misery equal to my own unhappiness, I can't balance the scales! That's how it is when you're a demon! And we'll kill anyone who tells us otherwise! 

Back with your group... 

You, Tanjiro, and Uzui were clashing with Gyutaro, who you knew had the advantage over Uzui. 

(Y/N): Uzui may have a high resistance to poison. But he's not immune like I am! Tanjiro! Let's move! 

Tanjiro: Why? What's going to- 

You pulled him out of the way as a swarm of sashes rained down. 

(Y/N): It's Daki! 

Up above... 

Ruby: That's a lot of sashes! 

Daki: HAHAHAHAHAHAHA! Now that my brother is here, I can go all out! 

Yang and Inosuke: OH SHUT UP ALREADY! NO ONE GIVES A CRAP ABOUT WHAT SKILLS YOU HAVE! 

Daki: AAAAAAAAAAAAAAAAAAAAAAARGH! 

All six of them began slashing and punching against Daki's sash attacks. 

All while below, Uzui was using his exploding beads. 

Uzui: This guy fights like a praying mantis alright! 

(Y/N): LOOK OUT! 

You and Tanjiro blocked the blood sickle blades as Uzui prepared for- 

Uzui: SOUND BREATHING: FIFTH FORM: STRING PERFORMANCE! 

(Y/N): Now that's a flashy move! 

The blood blades were also affecting Ruby's group! 

Weiss: What the?! These are-

Inosuke: Where did these things come from? 

Daki: HA! LOOKS LIKE GYUTARO IS GIVING ME A HAND! 

Ruby: Those two, they make a good team! 

Yang: Guess I'll give them this. They love each other like real siblings should! 

At that moment, Hinatsuru appeared and fired kunai at Gyutaro! 

Gyutaro: HOW ANNOYING! BLOOD DEMON ART: RAMPANT ARC RAMPAGE! 

He deflected them all and they went into Uzui! 

Gyutaro tried to attack, but Uzui ducked and cut off Upper Moon 6's legs! 

Then a kunai went into his neck! 

Gyutaro: What?! My legs ... these kunai must be coated in wisteria! 

(Y/N): NOW! 

You three all charged at him to finish the bastard off, but then- 

His legs regenerated! 

(Y/N): NO! 

Gyutaro: Nice try, but not good enough! BLOOD DEMON ART: FLYING BLOOD SCYTHES! 

He spun his arms like crazy as massive blood streams came out of them. 

(Y/N): DAMN IT! 

You coated yourself in Haki to protect yourself, and shielded Tanjiro from an attack! 

Then Uzui rushed in to make his chance work! 

Uzui: SOUND BREATHING: FOURTH FORM: CONSTANT RESOUNDING SLASHES! 

He unleashed a massive wave of explosions with his blae attacks, but as the smoke cleared, Gyutaro was nowhere to be seen. 

Uzui: What th- HINATSURU! 

Hinatsuru: Tengen! Don't worry about me! Find the- 

Gyutaro grabbed her by the throat! 

(Y/N): SHIT! 

Uzui: HINATSURU! 

He rushed to save his wife, but Daki's sashes got in the way! 

(Y/N): COME ON TANJIRO! 

Tanjiro: RIGHT! 

You and Tanjiro continued to cut through the sashes as Gyutaro tried to break Hinatsuru's neck, though- 

(Y/N): FLAME BREATHING: ESOTERIC ART: NINTH FORM: RENGOKU! 

You greatly injured Gyutaro and- 

(Y/N): GUM GUM RED HAWK! 

You punched him, sending him flying across the roof! 

Gyutaro: That ... speed. 

(Y/N): COME AT ME GYUTARO! LEAVE HER OUT OF THIS! YOUR FIGHT IS WITH US! 

Gyutaro: YOU FUCKING BRAT! DON'T INTERFERE! I CAN'T STAND PEOPLE LIKE YOU WHO GET EVERYTHING, WHILE I JUST SUFFER! 

As you prepared for his attack, Uzui came in from behind! 

Uzui: (Y/N) (L/N)! I OWE YOU MY LIFE! 

Back with Ruby's Group... 

Weiss: Guys! Nothing is working! Dabi's sashes are not letting us get close to her! 

Zenitsu: Calm down! We don't have to cut her head off at exactly the same time as the others! WE just have to make sure the two demons' heads aren't connected! Even after they take Gyutaro's head, we keep attacking. 

Yang: Zenitsu? 

Ruby: Is he- 

Inosuke: I LIKE IT MONITSU! YOU'VE GOTTEN BADASS! 

Soon... 

You, Tanjiro, and Uzui all slamed your blades onto Gyutaro's neck! 

Gyutaro: USELESS! I WON'T LET YOU TAKE MY HEAD! 

He twisted his neck and bit into Uzui's blades! 

Uzui: HANG IN THERE! 

Gyutaro launched himself off and pushed Uzui! 

(Y/N) and Tanjiro: UZUI! 

Hinatsuru: LOOK OUT! 

She pushed you two out of the way as the others appeared. 

(Y/N): You guys!! 

Ruby: Don't worry about us! She's weaker than her brother! 

Zenitsu: Can you still move Tanjiro? 

Tanjiro: Yeah! But the enemy poisoned Uzui so he's in trouble! If we don't finish them as quickly as possible- 

(Y/N): Then let's hurry! 

Ruby: HERE WE GO THEN! WEISS! BLAKE! YANG! ZENITSU! 

They all attacked the sash over and over! 

Weiss: WATER BREATHING: THIRD FORM: FLOWING DANCE! 

Zenitsu: THUNDER BREATHING: FIRST FORM: THUNDERCLAP AND FLASH: EIGHTFOLD! 

Ruby: GO FOR IT INOSUKE! 

Inosuke charged straight for Daki! 

Inosuke: HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA! THIS IS IT! BEAST BREATHING: SIXTH FANG: PALISADE BITE! 

Inosuke slammed both his blades into the sides of Daki's neck and decapitated her! 

Ruby: YES! 

He then grabbed Daki's head. 

Inosuke: I've got this, you guys! You help the old guy! 

Ruby: THANKS INOSUKE! 

Blake: He's a lot more reliable than I originally thought! 

Daki: YOU STUPID PIG! LET ME G- 

He punched her in the face. 

Inosuke: JUST SHUT UP ALREADY! YOU'RE FULL OF TRICKS, BUT THEY'RE REALLY WEAK WHEN YOU'RE JUST A HEAD! HAHAHAHAHAHAHAHAHA! 

But then Inosuke was stabbed by Gyutaro! 

Everyone: INOSUKE! 

You then turned to see Uzui on the ground, coughing up blood. 

Gyutaro: You fuckers are so pathetic! 

He then stomped on Tanjiro. 

Gyutaro: AND YOU'RE THE BIGGEST LOSER OF THEM ALL! YOU'RE EVEN FAILING TO PROTECT YOUR SISTER! SHE'S JUST A DEMON AND YOU'rE HUMAN! Oh well what can you do?! 

He broke two of his fingers! 

Gyutaro: WORM! DIMWIT! COWARD! LOSER! WHY WERE YOU EVEN BORN?! Say, why don't you become a demon for your sister? Yeah, that would be good. Then you'll both be the same! So how ab- 

Tanjiro headbutted Gyutaro! 

Gyutaro: AAAAAAAAAAAARGH! 

And then- 

(Y/N): EAT THIS! 

You stabbed him with all of the kunai that Hintasuru fired at him! 

Gyutaro: WHAT?! THEY PLANNED ON THIS?! 

Tanjiro then slammed his sword onto Gyutaro's neck! 

(Y/N): GO FOR IT TANJIRO! 

Daki: NO! BROTHER!! 

But she had little time to react to- 

Ruby: YOU THINK WE'LL GIVE UP SO EASILY?! 

Weiss: THINK AGAIN BITCH!!! 

Ruby and Weiss clashed with Daki over and over as Ruby slammed her Nichirin Blade onto Daki's neck! 

Daki: NOT THIS TIME! I WON'T LET YOU CUT ME! 

(Y/N): TANJIRO! FINISH HIM OFF! 

Tanjiro: Ignore the pain! STAY FOCUSED! COME ON! 

Then you noticed- 

(Y/N): HOLY CRAP! HIS SCAR! 

Daki tried to hit Ruby, but Blake, Yang, Zenitsu, and Inosuke cut up her sash again and again. 

Daki: WHAT THE?! 

Inosuke: DON'T YOU KNOW?! I CAN SHIFT MY INTERNAL ORGANS! AND POISON DOESN'T WORK ON ME LIKE WITH (W/N)!! 

(Y/N): STILL NOT MY NAME! 

Daki: BIG BROTHER! HELP ME! 

Tanjiro and Ruby: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAARGH! 

You cheered as both Daki and Gyutaro were decapitated! 

Their heads rolled across the ground as they faced each other. 

Makio and Suma found the others as Suma cheered. 

Suma: HINATSURU! THEY DID IT! I BET THAT HAS YOU ROLLING IN YOUR GRAVE! 

Makio: IDIOT! DO YOU KNOW WHAT THAT MEANS?! 

Then all of a sudden, you noticed something! 

(Y/N): BLACKWHIP! 

You pulled everyone away as giant poison bursts erupted out of the ground! 

Soon enough... 

You had healed everyone up.

(Y/N): Hey, is everyone okay? 

Ruby: Is it over? 

Tanjiro: Did we- 

(Y/N): It looks like it. I can sense the chi of Daki and Gyutaro fading. 

Tanjiro: We have to collect the blood! 

(Y/N): Why? 

Tanjiro: I know someone who can do analysis on the blood! 

(Y/N): Oh that's good. 

Soon... 

Tanjiro collected the blood of Daki and Gyutaro as you heard the two arguing. 

Daki: WHY DIDN'T YOU SAVE ME?! 

Gyutaro: WHAT DO YOU THINK?! ONE OF MY OPPONENTS WAS A HASHIRA! 

Daki: YOU COULD HAVE FINISHED HIM OFF SOONER! 

Gyutaro: I WAS TRYING TO! THE KID WITH THE EARRINGS WAS STILL MOVING! YOU COULD HAVE FINISHED HIM OFF! 

Daki: YOU COULD HAVE TOLD ME SO! YOU DIDN'T DO ANYTHING BUT LET YOUR GUARD DOWN! 

(Y/N): They're on death's door. 

Gyutaro: If you're going to call yourself an Upper Moon, you could at least beat a couple of wounded punks idiot! 

Daki: Oh yeah? WELL I BET WE'RE NOT RELATED BY BLOOD! YOU'RE PLAIN UGLY! 

Gyutaro: WHAT?! YOU'RE JUST A LOSER! YOU'D BE NOTHING WITHOUT ME! YOU WEAKLING! I WISH I NEVER PROTECTED SUCH AN UGLY HARPY LIKE YOU! IT'S ALL YOUR FAULT I SUFFERED! I ALWAYS END UP HAVING TO WIPE YOUR ASS FOR YOU! I'D BE BETTER OF IF- 

(Y/N): STOP! 

They both faced you. 

(Y/N): Just stop. I know you both love each other. Don't go out like this. You're all you've got. No one else can forgive you for what you did. All the people you killed hate you and curse you. All you have is each other. Just- 

Daki: Don't even think about lecturing us! I- I- 

She began to cry. 

Daki: GYUTARO! HELP ME! IT HURTS! I CAN'T! I- 

She disentigrated. 

Gyutaro: UME! 

He then remembered everything. 

Gyutaro and Daki grew up in the lowest caste of the Entertainment District. His body was weak, and he clung to life. He was persecuted for his looks. 

Everyone loathed him and called him a monster. Whenever he was hungry, he ate insects and mice. Then Ume his sister was born. 

Gyutaro finally had someone who loved him for who he was. 

He embraced his looks and swore to protect his sister. 

Then when Ume turned 13, she stabbed a customer in the eye with a comb. That man was a samurai. And for that she was burned to death. 

Flashback... 

Gyutaro: NOOOOOOOOOOOOOOOOOO! IT'S NOT FAIR! TAKE ME! NOT MY SISTER! SHE DOESN'T DESERVE THIS! PLEASE! NO! GODS! BRING ME BACK MY SISTER! SHE'S THE ONLY ONE I HAVE! 

???: Oh, is that so? 

Muzan appeared before him. 

Muzan: Swear your allegiance to me. And if you do, you'll become a demon. And I will save her life. What do you say? 

Without a second though, Gyutaro agreed. 

Present... 

Gyutaro: I don't have any regrets. But Ume, if you'd belonged to a better family, you could have had everything. The one regret I have ... is that I ... failed you. 

You could only watch as he disentigrated. 

And then you ... cried. 

(Y/N): (crying) Gyutaro ... Daki ... I hope you both find peace in the next life.