Muzan growled like an animal as soon enough, he was getting overwhelmed with sword swing after sword swing! 

Even then, he still had the whips on his back and his two arms swinging desperately! 

(Y/N): COME ON GUYS! KEEP IT UP! 

Muzan: NOOOOOOOOOOO! THIS ISN'T THE EN- 

But as he slashed, he noticed that all of the Hashira were able to stab him with their weapons turning red. 

Muzan: WHAT'S GOING ON?! DAMN! Compared to that man, they're still nothin- 

But then all of a sudden, his whips were cut off! 

Ruby: Ha! Nice one Zenitsu! 

Zenitsu had used Thunderclap and Flash to slash off his whips! 

Muzan: Have you forgotten that I can regenera- 

However, he then began to feel himself getting slower. 

Muzan: HUH?! 

Suddenly, he was getting hit more and more. 

Muzan: How's it possible?! HOW CAN I JUST AGE?! Is this because of the drug that Tamayo injected me with? What did she put into me? It's almost as if I've aged rapidly. Is this because of my white ha- 

(Y/N) and Tanjiro: HINOKAMI KAGURA: BENEFICENT RADIANCE! CLEAR BLUE SKY! FIRE WHEEL! RAGING SUN! FLAME DANCE! 

You and Tanjiro kept hitting Muzan again and again with the Hinokami Kagura techniques without letting up! 

Muzan: STOP IT! STOP MOVING A- 

(Y/N): DANCE! SETTING SUN TRNSFORMATION! 

Tanjiro: BURNING BONES, SUMMER SUN! DRAGON SUN HALO HEAD DANCE! SUNFLOWER THRUST! 

Muzan was being overwhelmed! 

Then you saw- 

(Y/N): Looks like you were wounded. 

You saw scars over Muzan. 

Muzan: DAMN WORMS! THEY KNOW! 

(Y/N): Those scars are the reason why you went into hiding. 

Muzan: DAMN YOU! 

He starts to run. 

Tanjiro: He's trying to escape! We can't let him go! 

(Y/N): OH NO YOU DON'T! 

You charged to Muzan and then dodging all of his strikes, you stabbed your Nichirin Sword into his neck and he felt- 

(Y/N): SILVER METAL OVERDRIVE!

Muzan: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAARGH! 

His body was burning. 

Muzan: WHAT DID YOU DO TO ME?! 

(Y/N): I think my Hamon is making Tamayo's drug activate more and more. Muzan! 

Muzan: AAAAAAAAAAAAAAAAAAAAAARGH! 

(Y/N): He's still- 

You and Tanjiro were on the dodge again, but- 

(Y/N) and Tanjiro: AAAAAARGH! 

Muzan: DAMN HUMANS! I WILL NOT DIE HERE! 

???: FLOWER BREATHING: FIFTH FORM: PEONIES OF FUTILITY! 

Ruby and several of her clones stabbed Muzan, knocking him back! 

(Y/N): RUBY! 

Ruby: MUZAN! AFTER EVERYTHING YOU DID, YOU DIE HERE! 

Muzan: WHY Y- 

Weiss: ICE BREATHING: ELEVENTH FORM: AVALANCHE! 

Inosuke: BEAST BREATHING: FOURTH FANG: SLICE N DICE! 

(Y/N): WEISS! INOSUKE! 

Weiss: GIVE BACK ALL THE BODY PARTS YOU TOOK FROM THE DEMON SLAYERS YOU SLAUGHTERED! 

Inosuke: OR YOU'LL PAY FOR IT WITH A MILLION DEATHS! 

Then out from the shadows came- 

Blake: HURRY YOU GUYS! 

Zenitsu: FINISH HIM OFF ALREADY! 

Yang: KILL THIS BAST- 

Blake, Zenitsu, and Yang: AAAAAAAAAAAAAAAAAARGH! 

The three were smacked to the side by Muzan!

Tanjiro: DAMN IT! Muzan! You bastard! 

Blake: SHADOW BREATHING: FOURTEENTH FORM: LUNAR ECLIPSE! 

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

Yang: FISHMAN KARATE: DEMON BRICK FIST: SUNLIGHT YELLOW OVERDRIVE! 

(Y/N): EVERYONE! GO FOR IT! 

You started to create Shadow Clones as they healed all your comrades with Mimic, and then- 

(Y/N): HINOKAMI - 

Tanjiro: KAGURA- 

(Y/N) and Tanjiro: BURNING BONES, SUMMER SUN! FIRE WHEEL! RAGING SUN! BENEFICENT RADIANCE- 

Inosuke: SIXTH FANG: PALISADE BITE! 

(Y/N): FAKE RAINBOW! 

Tanjiro: CLEAR BLUE SKY! 

Ruby: PLUM DANCE!

Zenitsu: THUNDERCLAP AND FLASH! 

Weiss: ICE AGE!

Blake: ASTRAL MOONBOW! 

Yang: CRIMSON RED OVERDRIVE! 

(Y/N) and Tanjiro: SUNFLOWER THRUST!! 

Muzan was pinned down! 

Muzan: DAAAAAAAAAAAAAAAAAAAAAAAAAAAAMN Y- 

His arms were cut off! 

Everyone: HUH?! 

???: YOU BIG JERK! 

Mitsuri cut them off! 

(Y/N): MITSURI! 

???: WIND BREATHING: EIGHTH FORM: PRIMARY GALE SLASH! 

Tanjiro: Mr. Shinazugawa! 

Muzan was turning inside out! 

Muzan: NOOOOOOOOOOOOO! THE SUN! 

He tried to move back, but then- 

Muzan: AAAAAAAAAAAAAAAARGH! 

His neck was grabbed by the chain of Gyomei's weapon! 

Gyomei: FACE YOUR DEATH AND REPENT! 

Muzan: Y- 

Giyu: WATER BREATHING: TENTH FORM: CONSTANT FLUX! 

Obanai: SNAKE BREATHING: FOURTH FORM: TWIN HEADED REPTILE! 

And then- 

(Y/N): MUZZAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAN!

You charged towards him, and- 

https://youtu.be/3lTcZL9J5ow

(Y/N): IT'S OVER FOR YOU! FACE THE LIGHT! 

You punched his head as he faced the sun! 

Muzan: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAARGH! 

He started to disintegrate! 

Muzan: THIS CAN'T BE! I'M BURNING! I WAS SUPPOSED TO LIVE FOREVER! STOP TH- 

His tongue was cut off by you! 

(Y/N): Stop whining and face it with dignity, you asshole. 

With that, Muzan was gone. 

The sun shone brightly as all of the Demon Slayers could finally rest. 

(Y/N): It's over! It's finally over!