Demon Slayer AU

By: FunahoMisaki

(A/N: I own nothing and it was just a little blurb that hit me so I had to write it. Maybe a bit OOC.)

Tanjiro grit his teeth as he did his best to continue to use the Sun Breathing Style in order to either kill Muzan or buy them time until morning came.

Muzan…the man who destroyed hundreds, no thousands or lives! The one who killed his family and turned his sister into a demon. The one who created the Twelve Demon moons and killed some of the ones Tanjiro called his closest friends.

Shinobu, Tamayo, Genya, Muichiro-

"RAHHHHHH!" There was a loud roar from nearby as part of the ground seemed to explode and the entire battle stopped as everyone looked over alarmed to see who this new player in the game was.

Everyone was treated to the sight of Muichiro bursting from the ground with her lower half now reattached and her eyes slit with visible fangs in her mouth.

Muichiro was now a demon.

Her slit eyes roamed around and landed on all of the injured and dead Corps members before they snapped to Muzan as she growled.

"It looks like I have a New Moo-"

SLAM!

Everyone gaped as Muichiro's fist slammed into Muzan's cheek and sent him flying into a nearby building.

"T-Tokito-san?" Tanjiro asked staring stunned at Muichiro who was crouched there growling angrily before her head snapped to him and her eyes lit up. A bright sunny smile came to her face as she darted to Tanjiro and slammed into him, nuzzling her face against his cheek happily.

"Muichiro! Call me Muichiro!" Muichiro said cheerfully and everyone was gaping at her in disbelief while Tanjiro laughed a bit at how ticklish it was.

"Alright. I will." Tanjiro said glad that she was still alive even if she was now a demon, it was fine though. Tamayo and Shinobu had made the cure after all.

"Now let's get an advantage. I can only do this once." Muichiro said before she bit her hand and ripped open the skin.

"Blood Demon Art! Heal and Revival!" Muichiro called and it seemed as if a film covered everyone and everything for a little while, Muzan bursting out of the building looking furious before he froze. Tanjiro felt as his body began to go back to normal, the deformities seeming to reverse back into nothing and his strength returned to full force.

"Ugh my head."

"What hit me?"

"I think it was a demon lord."

"Guys I think we all died!"

"Shut the fuck up Carl."

"Ow…that hurt." A more familiar voice groaned as two figures and then slowly more began to stagger from the hole in the ground that Muichiro had made.

"Genya-kun!" Tanjiro was happy to see his friend back alive as the fallen Corps members began to rise, their injuries sealing shut and their fallen limbs reattaching.

"Onee-san!" Kanao immediately rushed to her older sister while Muzan began to cough and bubble violently. Everyone immediately tensed before their eyes widened when something seemed to burst out of his side. A form…a very familiar form.

"What? How am I? Hadn't I been…" Tamayo looked around and then down at her hands confused and alarmed before she glanced up at a furious Muzan and quickly jumped away.

"So a Blood demon art that heals and revives your allies? Impressive and useful." Muzan said locking his eyes onto Muichiro who flipped him off immediately.

"And only able to be used once. By someone who will never consider you an ally." Muichiro said firmly as she glared at Muzan.

"Then you're an enemy." Muzan said extending his hand to her and squeezing it into a fist. She just gave him a flat look.

"No shit." Muichiro said completely unaffected by whatever he had tried to just do.

"What? How?! You have my blood in you! I should be able to detonate those cells!" Muzan seemed outraged and stunned while Tanjiro held his sword firmly and everyone was more than ready to fight some more and keep the asshole busy until sunrise.

"Fuck you that's how." Muichiro said making more than a few people snort slightly, including Tanjiro, as they stood side by side ready to face down Muzan.

"Someone throw me a sword, mine was left underground." Muichiro said and immediately an indigo colored sword was thrown her way, her snatching it out of the air and taking a deep breath.

"Congratulations Muzan. You've got seven Hashira one who is now a demon, four Hashira inheritors, one feral gremlin with swords, more than a dozen assorted Corps members, and two demons all against you and only forty five minutes until sunrise." Muichiro said with a dangerous smile on her face as everyone got prepared to fight.

"And you were doing your best to injure or kill my mate. You're fucking dead." Muichiro said her slit demon eyes glinting dangerously while Muzan seemed to realize just how close sunrise was.

And with his body still fighting off the aging effects and who knew what else was in Tamayo's poison…

Even he could admit that this didn't look good, not that it mattered. After all he was a superior life form and would not be stopped by these mere humans.

There was no way he was going to die here. Even if it meant fleeing!

"Cut off any chance he has to escape! If he gets away he'll stay underground for a hundred years!" Tamayo yelled out and the Corps members obligingly spread out to cover any exit routes.

"It seems that you are truly routed now Muzan Kibutsuji. I told you that this ended tonight." A familiar voice called across the crows and Muzans eyes widened in disbelief while the other Corps members eyes widened and they were happily surprised but didn't dare take their eyes off of their enemy.

"Ubuyashiki…" Muzan growled dangerously and angrily.

"Ara? Didn't I tell you that my ability has a twelve hour time frame? Those I consider family or allies who's been injured or deceased within the last twelve hours are healed and brought back, within a certain radius of course but considering we hadn't moved even two miles yet…" Muichiro smirked at him and Muzan's eyes landed on her with a furious growl.

"Must have slipped my mind." Muichiro said shrugging slightly and Tanjiro grinned at her.

"It truly is amazing what your ability was able to do Muichiro-chan. Now then…I believe this has dragged on long enough. Everyone! Keep him busy until the sun rises! Do not let him retreat or escape at any cost!" Kagaya ordered across the crows.

"Yes Oyakata-sama!" All of them replied in one voice and the Hashira immediately went on the attack, Tamayo jumping in with truly fierce punches or kicks on occasion but mainly seeming to focus on patching up those who got hurt.

Against seven full strength Hashiras, one of whom was now a demon, and four Hashira heirs along with their feral gremlin boar friend?

Muzan was finding it hard pressed to get time to attack them properly, much less escape to find shade.