The bond between two siblings

The final fight

Narrator pov:

Muzan had been engaging with the pillars, all his uppermoons are dead. But he knew something was off, because nakime brought all the pillars to him without his command. That was when he realized, nakime is being controlled, by tamayo's pet. "YOU WILL PAY FOR WHAT YOU'VE DONE MUZAN!" yushiro yelled while keeping his blood demon art on nakime and able to control her by creating illusions. As suddenly his head was decapitated and he regenerated a few seconds shorter than before and that was when he saw his arm suddenly falls off.

Muzan pov:

Someone's invisible, my arm, it burns! Kamado nezuko, where is she?! "Breath of the wind Sixth Form: Black Wind Mountain Mist" it was the wind pillar, what a pest! Nakime, you are hear by dead.

Narrator pov:

Nakime was suddenly killed causing the entire fortress to collapse. Everyone woke up and they were outside, in a town, its good though because now they have to wait till sunrise! "Nezuko!" Tanjiro yelled while finding her, he found the rest of the hashiras and they were looking for muzan as he suddenly appeared behind tanjiro "TANJIRO LOOK OUT!" screamed giyuu but tanjiro turned around only to have his entire head blown off. "YOU BASTARD!" genya yelled before shooting muzan in the face, "fool... your a false demon" muzan said as he nearly killed genya if it hadn't been for sanemi using a breath form "DAMMIT GENYA!" Pay attention! As he suddenly stabbed gyomei's shoulder but he had muzans tentacles destroyed only for them to heal again. Then his arms were cut off and were healing slower now.

He slashed something with his tentacle and he destroyed the blood demon art and saw nezuko "dance of the fire god! Sunflower Thrust!" The user unleashes a single thrust attack with the point of the blade. But before that muzan saw his battle scars opening and he was getting slower, like as if he was getting older!

Muzan pov:

Dammit, tamayo! What the hell did you do to me! 'Figure it out! You have 5 brains!' Tamayo said with a large grin.

Narrator pov:

Flashback

Tamayo and shinobu had been working on a drug with, wisteria, make him age, and a drug that will weaken him and the serum that can turn demons into humans.
"Oh tanjiro" tamayo called "we have it, the serum, it will make you human" but tanjiro declined "i cant be human for the fight against muzan" tanjiro responded

End of flashback

Yushiro and 3 slayers dragged tanjiro's lifeless body to an alleyway where he can heal. But tanjiro wasn't healing, "dammit! Come on tanjiro!! Why wont you heal!" Murata asked. "A hit from muzan, its whats keeping him from regenerating" yushiro responded "he's still alive though" as yushiro injected tanjiro with a serum that can heal demons wounds in an instant but it wasn't working, yushiro injected another one, it still wasn't working, but one more shot and tanjiro's heads began to heal.

"Breath of flowers, sixth form: whirling peach!" Kanae and kanao yelled as they both attacked muzan cutting of his limbs. "Breath of stone: First Form: Serpentinite Bipolar" Gyomei throws both the flail and axe towards their intended target and manipulates the chain by rotating it thus causing the axe and flail to also rotate in order to drill and grind right through his target. As muzan launched all his tentacles at gyomei but giyuu came in "breath of water, eleventh form: dead calm" and the tentacles that should've stabbed gyomei were cut off but some of the tentacles still hit the two pillars. Until one tentacle was about to stab kanae but misturi came "PLEASE! STOP!" she yelled and she was really angry that she used her bear hands and ripped one of muzans entire tentacle off.

But suddenly muzan used an attack that knocked everyone back and not only that it really injured all the hashiras and killed a lot of slayers. Some hashiras injured more than others obanai had his eyes slashed, muichiro lost his arm, Giyuu was paralyzed for a while. Kanao found herself in front of muzan "KANAO!" nezuko screamed until right at the moment tanjiro came back "Breath of the moon, twentieth form: Cataclysmic Calamity, Lunar Extinction" Tanjiro unleashes a devastating barrage of slashes and stabs in all directions with the swords emanating from his body within an extremely large radius that decimates anything it makes contact with. It destroyed muzans upper body but he was healing fast.

Genya found one of tanjiro's broken blades, he immediately ate the blade and got up as his gun now looked warped, he pointed it at muzan and shot a powerful bullet, and soon not only muzan found himself weakening but he also saw his battle scars, and he soon saw blades growing out of his body. "THATS MY LITTLE BROTHER!" Sanemi yelled as mist appeared and surrounded muzan, and one of his scars were slashed, and he saw muichiro and stabbed muichiro with his tentacle and threw him to the side. Then what seems to be a giant snake appeared and was about to slash another battle scar, he tried to use his tentacle only for his tentacle to be ripped off by misturi again. Then he hit his battle scar, "i dont need my eyes" obanai said and muzan tried to kill him but tanjiro protected him.

Tanjiro's eyes now looked like kokushibo's eyes and nezuko appeared cutting of all of muzans tentacles and nezuko reminded muzan of 'yoriichi?!' Muzan thought he was now afraid.
"Breath of the moon, twenty first form: eternal night" then he saw tanjiro's blade as what seems to be two dragons forming from the crescent like blades and one hit and at the same time from nezuko
"dance of the fire god, Dragon Sun Halo Head Dance" Nezuko unleashes a continuous fast and powerful sword attack that seemingly takes the form of a flaming sun dragon. This technique is capable of decapitating multiple enemies at once.
Then muzan realized all the pillars were all attacking at once,
"breath of stone, Fifth Form: Arcs of Justice"
"breath of love, Sixth Form: Cat-Legged Winds of Love"
"breath of water, tenth form: constant flux"
"breath of flowers, final form: Equinoctial Vermilion Eye" from kanae
"breath of wind, Ninth Form: Idaten Typhoon"
"Breath of mist, Seventh Form: Obscuring Clouds"
"Breath of the serpent, Fourth Form: Twin-Headed Reptile"
Even zenitsu who gathered up the last of his strength and inoskue
"Breath of the beast Tenth Fang: Whirling Fangs
"Breath of thunder first form: thunder clap and flash, GOD SPEED"

With all attacks colliding on muzan and muzan saw the sun and it was rising in him. Muzan had turned into what seems to be a giant baby, as an attempt to keep him there the remaining slayers all pushed a train onto muzan and with all the hashiras strength to keep on attacking him, to make sure he stayed in the sunlight. Eventually it was now down to nezuko and tanjiro to keep him there. They had succeeded and muzan was now nothing but ashes, but tanjiro was turning into ashes from the sunlight, there was no shade for him to hide. "TANJIRO!" nezuko yelled "PLEASE DONT DIE ON ME." as when they embraced into a hug while tanjiro was embracing it, tanjiro couldn't heal all his wounds, and the sun was burning him, but at that moment kanao injected the serum into tanjiro, turning him back to human. It was now safe for tanjiro.

The kakushi were tending ti the remaining hashiras, muichiro succumbed to his injuries because of a stab from muzan, gyomei also succumbed to his injuries and told the kakushi to save some other children as he saw a vision of the children he took care of before. Obanai and mitsuri died together and promised they'd be with each other in the next life. Kanae was now like kanao, both of their left eyes weren't working from using the final form, inoskue and Zenitsu were fine but severely injured. Tanjiro still had to tend to his injuries but he was now human, nezuko as well had to tend to her injuries. The 4 remaining hashiras who survived from the fight were : kanae, shinobu, sanemi, and giyuu. But they had won, and all the hashiras who died during the battle all died with a smile.