Inside the protection Muzan had created for himself while he dissolved Tamayo's poison, the King of Demons gasped in shock. He'd been keeping track of the different fights as best he could while portioning the rest of his focus on the poison, but all of him froze at the new revelation.

Kamado Tanjiro was a progenitor?

How?

Did he find or recreate the medicine that had turned Muzan all those years ago? Had he found the blue spider lilies?

Did it matter at this point?

Now the boy needed to die more than ever. Which meant Muzan would need to finalize the plans he already had in place. Because the boy would come, and Muzan would have to take care of it now or risk said boy becoming a real threat to him. He hated it, but he had no choice.

Fine.

The boy wanted to fight, progenitor to progenitor? Muzan would oblige.

And that also meant that the demon who looked like Akaza was, in all likelihood, his missing Waxing Third. He'd likely thrown off Muzan's curse because the other boy had threatened him or used some sort of blood art on him to turn him to his side.

He would regret it. They both would.

Muzan would make sure of that.

About then, he realized that he'd lost concentration on the poison and it had begun to erode his cells again. Gritting his teeth, he pushed his future plans to the side for now. He had everything in place for the most part. He just needed to show the other 'progenitor' who was the strongest – who would always be the strongest because he had 1000 years on everyone else!

There was no chance they would win today, and he'd just obtained the key to conquering the sun.

His victory was assured.

It was only a matter of time.

"Come then, Kamado Tanjiro," he said to no one, eyes glowing in the darkness. "Come meet your fate."

xXx

"We've got the whole system completed," Kanata said from her desk.

Kiriya nodded in affirmation, feeling a small sense of relief at that. At least they had as many eyes as they could possibly get inside the enormous mansion. It continually changed and warped, but they were keeping track of it as best they could. It was better than nothing. It was also… more than a little strange, choosing to see something that wasn't actually in the room with him, but it was also a brilliant idea and they were definitely getting the hang of it.

"I have eyes on multiple Hashira," Kuina spoke up on his right.

"Hai," he said in acknowledgment. He wished he had an entire map of the place – even if it was only a basic one – to really go off of, but they would just have to do their best to keep track of everyone's positions with what they had.

"Name the Hashira you're watching," he called.

"Himejima-san and Rengoku-san," Kanata said succinctly. "They have found and are trying to take on Waxing Three."

"Shinobu-san, Kanroji-san and Obanai-san," Kuina said immediately after. "The latter is not in good shape. I believe he has been injected with demon blood by a Waxing Moon."

Kiriya's grip on his paintbrush tightened. "I see."

"Obanai-san is currently with Akatsugi-san and another demon I don't recognize."

The black-haired boy nodded again and jotted that down as quickly as he could. "I am currently watching Shinazugawa-san and Tokito-san fight Waxing One," he said as calmly as he could, then thought about everything he'd learned. "I am also keeping an eye on Muzan." He focused on the crow circling above the grotesque mass of flesh that hid Kibutsuji Muzan for a moment and had to repress a shudder. Fortunately, he had more than enough practice doing so.

"How many groups of non-Hashira demon slayers are you watching?"

"Six," Kanata said.

"Three," from Kuina.

"Four plus a group of Tsugukos currently taking on Waxing Five," Kiriya told them, "one of which has been injected with demon blood." He had come to the conclusion when they'd first discussed this plan that he wouldn't hold any information back from anyone. They needed everyone they could recruit to figure this out. Getting as much information out as possible to everyone involved would serve them the best. They didn't have time for secrets or pride here.

"Yushiro-san, did you hear all of that?" he asked aloud.

"Yes. Through your stupid crow."

Kiriya didn't know how the boy's demon blood art worked, but it really was amazing… and kind of frightening. It was also the key to coordinating everyone so they could take Muzan down, once and for all.

"Currently you are…" he paused and checked everything he could, "three floors up and a little west of Nakime. According to Kamado-san's report from last time, you will be needed there. Can you make it?"

"Of course I can!" came the reply.

"Good. We need you there as soon as possible."

"I'll get there. Pay attention to the fights," the demon boy replied acidly. He really was an unpleasant fellow, but Kiriya did his best to not let the words affect him. Said boy was helping them and so he would put up with his abrasive attitude.

And he would do it kindly. Like his father would have.

"Thank you. Be safe."

The boy didn't respond aloud, but Kiriya could hear him muttering something under his breath that he couldn't pick up. That… was probably a good thing.

Before he could say anything else, the crow they had circling above the ruins that was their house (Mother… Father… Onee-san and Onee-san… Later) spotted something moving towards the fires that thankfully had not spread. Said something shot through (or over, he couldn't tell from this high view point) the foliage towards the estate very, very quickly. Just what…?

And then Kamado Tanjiro came to a stop when he saw what had happened. Kiriya could hear the demon growl from where the bird flew. It was… scary. Very scary. Then the boy ran towards one of the shoji doors in the ground, obviously left to lure hashira in.

"Follow him, Yume," he told the crow. "Now! Hurry!"

The crow, thankfully, dove in time to catch up with the boy before the doors closed. He hoped she could keep up with him.

Part of him couldn't help but be relieved that another pillar had arrived, but part of him stubbornly held onto his worry and fear. The fight had only just begun and they still had at least six hours until dawn (thank the kami it was summer). They already had too many casualties and at least two people about to be turned into demons—

"Kocho Shinobu has been injected with demon blood while trying to save Hashibara Inosuke!" Kuina called out.

Kiraiya grit his teeth again. Make that three. If they weren't careful, Muzan could turn all of their slayers against them. Although it took longer to turn swordsmen, from what Kamado had said, that still took too many of their high-ranking officers out.

"Yume, direct Kamado to where Muzan is. Left, Right and up two levels."

"Hai, hai!" the bird said, then called out those exact instructions. Kamado slowed as he listened, then nodded and turned in the direction he'd been told.

Then the mansion moved again, taking Kibutsuji away from Kamado. Kiriya grit his teeth and told the crow to let Kamado know.

This… this could take a while. Both sides were stalling… but Kiriya had the feeling that the longer it took for Kamado to meet Muzan, the worse it would be for all of them.

xXx

"I see," Waxing One said as he towered over Shin-san, his blade now longer and sporting… arms? Branches? What? Muichiro grit his teeth and forced himself to stand, but then fell back to his knees. The surprise blows hadn't been fatal if he could control the bleeding, but they had been deep. He also wasn't used to concentrating on stopping the bleeding from so many places on his body at once. He may just have to bind them as best he could… if the demon would let him. He had some bandages he carried with him if he could find the time…

"It's him, isn't it," the red-haired demon said thoughtfully and then glanced at Muichiro. What was he…?

And then it clicked and the Mist Pillar's eyes honed in on the Wind Pillar. The Wind Pillar who should have healed already, but was curled over one knee, one hand holding his sword hilt so tight it shook on the ground and the other gripping his head. He grit his teeth but… Muichiro could see drool.

Oh.

Oh, this was not good.

"You want him, don't you," Waxing One went on. "A good meal… and I suppose I could let you have it and then turn him into a demon to save his life." He snorted. "Nothing distracts demons more than their food, after all. But you had such control over yourself. Why are you having such a difficult time, I wonder."

Well, if he insisted on just talking, Muichiro would take advantage of that. He quickly reached into the satchel he carried in the large pockets he'd insisted on for his uniform (a fabulous invention from the West that he highly approved of*). Then he assessed which wounds he should bind. If he bound the more serious ones, he'd have to take more care, which would take more time, meaning he'd be stuck with trying to concentrate on stopping more lesser wounds from bleeding once the fighting started again. If he bound the lesser wounds, he'd likely get to more of them which meant he'd have to spend less concentration on keeping fewer serious wounds from bleeding.

That was probably the best idea.

Nodding, he found the wounds on his legs and arms and side, carefully binding them as best he could and as quickly as he could.

"You were a Merechi, weren't you? When you were human."

The Mist Pillar tried to tune out the words of the demon, but it was difficult. He may have to fight two Hashira-level opponents now but had to focus on wrapping the wounds. All he could do at this point was listen.

"Did you know that a turned Merechi always craves blood more than other demons? I always found that rather amusing. They tempt demons more than any other, but as demons, are tempted more than any other. It's all you can do to not attack your comrade right now, isn't it." He didn't say it like a question.

Muichiro grit his teeth and moved onto the next wound he had to bind.

"You're a pathetic creature," the older demon went on. "Although it does make me wonder. How did you get the Slayer Corps to accept you if you have this kind of a reaction to blood? How many humans have you eaten? And why did they make an exception for you?"

Shin-san growled, letting out heavy breaths in his breathing pattern. "None."

A hum of surprise from the demon as Muichiro finished with his thigh and moved to his arm. That one would be trickier, but if he held one end in his mouth… yes. That would work.

"How did you, of all demons – false or not – manage that?"

"Ain't… tellin'," the white-haired demon replied, voice still guttural and raw.

Muichiro pulled the bandage tight and began to tie it.

"Then let me see you eat your first one."

The Mist Pillar had just finished tying that particular bandage when something grabbed the back of his neck. He yelped and grabbed for his sword, but couldn't reach it in time.

"NO!" he yelled, but the Waxing First didn't even acknowledge him.

"Here," the demon finally said, shoving Muichiro at Shin-san. The white haired man jumped away, holding a hand over his nose and shaking his head frantically.

"I won't let you kill him," Waxing One said, voice almost reassuring if it wasn't so mechanical. "Not when he can be of use to that man… and to me. So just a taste…"

Muichiro abandoned the bandages on his arm and reached up to try and pry the hand holding the back of his collar, to no avail. It felt like trying to bend metal with his hands. Even Hashira couldn't do that without a decent grip.

"Stubborn," the red-haired demon scoffed.

He walked forward, dragging a still struggling Mist Pillar with him. One moment, the demon stepped out. The next, everything blurred. Then Muichiro was shoved at Shin-san again, directly in front of him. Shin-san whose slitted eyes had gone a little glassy. He was losing himself, the Mist Pillar realized.

"Snap out of it!" he yelled, but the demon barely blinked, just staring at the human in front of him like he would a piece of meat, drool practically sliding down his chin.

"Consider this a parting gift before I destroy you," Waxing One said. Shin-san reached his clawed hand forward, shaking. Muichiro grit his teeth, bracing for pain and preparing to fight the white-haired demon off.

Shin-san licked his lips with that strange, purple tongue and bit his lip as if trying to restrain himself, but his slitted eyes had gone large and round – like a cat's right before they attacked.

And then he moved, lurching forward with his mouth open and claws outstretched.

Muichiro closed his eyes, pulling his arm back to punch and defend himself, but no pain came. He was jostled, and then he felt as if he were falling. Something caught him and then blurred speed to the other side of the room and…

What?

He blinked in surprise, then looked down at the arm holding him around his waist. Then he looked up at Shin-san, growling as he devoured a hand…

A demon hand.

Oh.

He glanced back where they'd come from to see the other demon with his overly-long sword in one hand looking down at the other appendage. Or lack thereof. It wasn't there. Then it was and he turned his blank expression on them.

"So that is how you've been surviving – by eating other demons. How despicable, even for a monster."

"I don't… want to hear that… from you," Shin-san said between swallows. Muichiro was grateful the man wasn't eating him but… he certainly classified that as gruesome.

"That's disgusting," he commented.

"You think I don't know that?!" Shin-san replied before he popped the last piece into his mouth. "But it ain't like I have much of a choice." He swallowed again. "'Sides, that arm alone filled me up better than whole other demons. Don't think I'll have too much of an issue not attacking you now."

That… could come from eating part of Waxing One, Muichiro supposed. Huh.

"You truly are an abomination," the other demon said as he turned to face them, all six eyes fixed on them.

"Oh, your sword," Shin-san said hurriedly as he shoved the object into his comrade's hands. Muichiro almost fumbled it, but managed to get a hold of it. "And prepare yourself. He'll be harder to beat now."

And then the white-haired man grinned.

Had he been this insane before he became a demon?

"Good thing I feel better than ever."

Then an arc of moon-shaped blades came streaming towards them.

xXx

Mitsuri pushed all other thoughts to the side as she left the victim in the hands of the demon slayers – of Miyabe and Imagawa (seriously, so cute… but now she had to focus) as she ran. She wasn't sure if coming across Shinobu had been lucky or by design, but the woman had been desperate to get back to the other demon slayer she'd left behind to fight Waxing Two.

The demon who had killed the former Flower Pillar – Shinobu's sister. Mitsuri hadn't met her, but she'd heard wonderful things about her from Rengoku-san, who had worked with her a couple of times before he'd become a Hashira. She couldn't blame Shinobu for wanting revenge for her sister. If someone killed Mitsuri's brother…

But Shinobu was fighting Waxing Two! The very demon who Mitsuri had met and… she had her own issues regarding the demon. She wanted to at least be a part of the fight that would take him out.

She closed her eyes, reaching out and sensing… there! She turned immediately right, and then left and kept running. If she just—

"NO! Kocho-san!" A voice shouted. Mitsuri bit her lip and hurried even faster.

Then a scream of agony – high-pitched and… that was Shinobu! Mitsuri's breath hitched for just a moment as she turned one final time. Was she too late?

Please don't let me be too late…

"I'll kill you!" the first voice said, both loud and low.

"Oh?" that all-too familiar voice that haunted her dreams returned.

Shinobu screamed again. At least she was alive, but what…?

Then the Love Pillar rushed into a hall that bordered on a large room filled with water and wooden bridges… or walkways? Lily-pads scattered in bunches over the top of the water that couldn't be more than a foot deep. In the center of the room, Waxing Two stood, facing a boy Mitsuri had never seen before.

Except… wait… was that what the boy with the boar-head looked like under the mask?

"Beast Breathing, Fourth Fang: Slice n' Dice!" Yup.

The boy unleashed several swings towards the demon, missing Shinobu who was sprawled on the floor in front of where said demon had just been, writhing. What had he done to her?!

The blond jumped over the boy's attack and went to land next to Shinobu again.

Oh, no he didn't.

"Breath of Love, Third Form: Lovecat Shower," she whispered to herself as she leaped into the air. He couldn't dodge in the air, could he?

Turned out, he couldn't. Not completely, at least. But he did sense her somehow, and was able to avoid her taking off his head. She slashed through his chest instead, but she'd somehow missed his arms (how?!) and he had his fans in hand. Mitsuri felt her feet touch the wood and already changed direction, scooping up Shinobu (not easy to do with her sword still in hand) and rushing to the other side of the room.

Behind her, she heard the other boy retreat as well, probably a good idea with the ice mist that froze the area they'd just been in.

"Oh?" Douma said as Mitsuri flipped, turned and landed facing the demon… who was already regrowing his body. At first she thought he'd be naked (ugh!) but he cared for his appearance so much he manifested clothes. Well, thank the kami for small favors, she supposed.

"Well, isn't this familiar? You fighting me at the side of a unique boy while protecting someone turning into a demon."

Mitsuri swore her heart stopped for a second. What?!

She looked down at Shinobu, still writhing in her arms… just like Nezuko had…

"Except this time," the demon said, "you don't have someone here to burn the cells out, do you? Now you'll have to make that choice."

Mitsuri grit her teeth and set Shinobu down. She tried to do it gently, but the other girl's thrashing made that difficult.

"Oh… have you decided to finally kill your comrade? Like a good Hashira is supposed to."

"Oi! Don't ignore me!" the beast-breathing boy shouted at the demon.

He did, watching the Love Pillar with that interested, amused, and all too condescending smile she hated. But she had an extra card up her sleeve – something Tanjiro had given to all of them on the way out of town before they'd heard about the attack on the Kamado family. (She suspected he'd been saving them for the supposed attack on the Swordsmith Village.)

Not wasting any time, she pulled the small flask of blood out. She knew this was risky – that it may not make anything better in the short term… but she had to try.

So she yanked the stopper out with her teeth, grabbed Shinobu's already fanged mouth and poured the contents past the other woman's lips.

"Wait, what are you doing?" Waxing Two asked.

"Yeah, what are you doing?" Inosuke also asked, confused.

"What I have to do," she said as she shoved the Insect Pillar's jaw closed and put a hand over her lips. She felt the other swallow. That would… either kill her or make it easier for them to save her later. And that was all she could do at the moment.

After that, Mitsuri stood and took a stance, practically feeling her mark manifest itself.

"Want to see how much better I've become?" she asked. Shinobu would have said it with a smile. Mitsuri couldn't bring herself to. She only stared the Waxing Moon down.

He frowned, glanced behind her at Shinobu and then back at her. Then he shrugged. "Sure."

And then they both leaped towards each other.

xXx

*Author's Note: Afaik the West did NOT invent pockets, but how they were incorporated into uniforms at the time, it would probably have been a pervasive belief.

Thank you to Found and Quathis for their help on this!

Also, thank you for the almost 700 Favs!

(There is fanart on my AO3, this story same name if you would like to check it out)

Discord: discord. gg/xDDz3gqWfy (no spaces)