Oh, boy, another crossover idea born out of a silly coincidence? Don't mind if I do!
In the streets of Tokyo sprawled a bustling street market. Civilians swarmed around during the brightly lit night, conversing cheerfully and pointing at various shops and stands. As more and more lanterns were lit as the night deepened, the light made the night sky almost glow orange.
Amidst the crowd of people walking aimlessly, indulging in their curiosity wherever they went, two particular people strolled around equally aimlessly. Although acting slightly more confused than your average civilian, they still… sort of fit in.
"Oryou-san does not like this place." a dark-haired woman said, shuffling along the ground after her partner had scolded her not to float in public. A pink ribbon rippled in the air, occasionally slapping the man following behind her in the face.
"Now, now, Oryou-san." a man dressed in a western, white suit with blue-striped hat said, patting the woman's back. "A job is a job, you know? And even if we did end up in normal Japan, it's fine! We'll return to our jobs as Counter Agents soon enough. But anyways, I'm sure that we're not just around for some random reason, and some great evil is just around the corn-"
Then, Sakamoto turned onto a streetway, accidentally walked into another guy, and tripped.
"Whoa!"
"Hey!"
Sakamoto fell flat to the floor, his hat covering his vision. Slowly, he got up, smoothing out rustled fabrics and aligning his hat with his head once more.
"Sorry about that." He said, closing his eyes smiling disarmingly. "I wasn't paying attention.
"You tripped Ryoma." Oryou growled menacingly, contrasting with Sakamoto's taciturn response. "How could you..."
"Oryou-san, no!" Sakamoto said, getting up quickly and putting a hand on Oryou's quivering shoulder. "I'm sure it was just an accident, sir…"
"Yeah… I apologize for my distraction." another man said. As they both looked up at each other, however, they froze.
Sakamoto immediately noticed the… extremely similar attire that the two were wearing. Other than the palette-swapped suit, their hats were practically identical, with the stranger's black stripe differing from his blue.
"Well, if that isn't a coincidence…"
"Indeed." Sakamoto said, looking into the man's oddly veined red eyes. Was there some sort of health condition that caused that? Because it certainly did not look healthy.
"Oryou-san does not like this man. He smells weird."
"And what a beautiful wife you have, sir." the man said, smiling.
"As do you." Sakamoto said, tipping his hat towards the woman carrying her own child.
"Oryou-san does like this man. His words are pleasing to me."
"I'm sorry about her." Sakamoto said, sheepishly. "She can be a bit childish sometimes."
"No matter, no matter." the man said, looking Oryou in the eyes. "Sometimes, the best people are just a bit-"
His blood red eyes met Oryou's soullessly black ones.
"Uh-um…" he stammered. "A bit… eccentric. W-we have to leave now."
"...Okay?" Sakamoto said, raising an eyebrow. "Alright, see you around!"
"Come on, darling, we have to go!" the man said urgently. Soon, they disappeared into the crowded Tokyo streets,
"...That was weird."
"Again, Oryou san must say that the man smelled demonic."
"Demons, huh?" Sakamoto said. "I mean, I was exaggerating when I said we would meet a great evil just around the corner, but-"
A hand clasped his shoulder.
Sakamoto slowly looked backwards. A boy wearing a blue shawl and a checkered haori stared at him intensely. In fact, Sakamoto could almost taste the animosity in the air.
He raised an eyebrow again. "Seriously? Is Tokyo this weird of a place?"
…
Tanjiro looked into the man's eyes. They were black and unassuming, but something was… unnatural about him. The scent from that night, however, the night where his family had died, was…slowly fading away?
"Is this little bug bothering you, Ryouma?" another being said. Tanjiro looked at the woman beside the man that smelled like a demon, and completely froze.
It was like a snake staring at its prey. The overwhelming, oppressive aura that was slowly leaking from the woman emanated across the courtyard, causing the passersby to stare more than they already were at the sailor uniform. Her eyes flashed red as she looked at his katana.
"Assassin?" she muttered? "Another one?"
Suddenly, the air around her began to ripple, as another scent began to emanate throughout the streets.
It was old. It was powerful.
And it smelled strongly of blood. Blood and poison, fire and death. It was the smell of century-old massacres plastered onto every fiber of the woman's being.
A dark, shadow aura began to spread on the ground, it was like ink soaking the soils. And Tanjiro finally realized what this was.
A blood demon art.
Which meant… that the woman was a demon.
Tanjiro looked around. The streets were much too crowded. Quickly, he turned and ran. He didn't want another city to be massacred. But one thing was clear.
The demon lord was hiding amongst mere humans. And even his mere minions were incredibly powerful.
Of course, just as Sakamoto shrugged and turned a street corner, Tanjiro had to run into a person who was turned into a demon.
He looked at the rapidly healing marks on the man's neck, and remembered the woman's long, sharp nails and how deeply she smelled of blood.
He swore vengeance on Muzan. And the next time he saw that man with his tacky suit and foreign attire, Tanjiro would drive his sword through the demon's neck.
…
"What do you mean you don't have any money?" the innkeeper yelled, brandishing a broom handle. "You come in here, with your fancy sword and your gun, but you don't even have a single yen to spare?"
"I'm-" Sakamoto spoke up, trying to placate the innkeeper.
"And what the hell is up with her, anyways? Trying to order frogs? What kind of place do you think this is?"
"I'm sorry, sir." Sakamoto sighed. Trying to shout over people had never been a particularly strong suit of his.
"Oryou-san wants to eat this bug." Oryou growled. "Can Oryou-san eat this bug?"
"What do you think you are, some kind of demon?" the innkeeper mocked. "Or are you going to pull out that puny little sword and stab me, huh?"
"No, Oryou-san! Please don't…" Sakamoto sighed, pushing Oryou down just as her hair began to flutter in an ephemeral wind. "We'll just go elsewhere. Thank you for your time!"
"But Ryoma-"
"We're leaving!" Sakamoto shouted, dragging the furious woman out of the store.
Slowly, Sakamoto dragged Oryou by the arm to somewhere that was more quiet. Around them, couples stared, before looking at each other and blushing. Old folks chuckled. Courtesans looked at Sakamoto, then at Oryou, and then sighed at their missed opportunity.
"They insulted you." Oryou said, growling. "That boy from earlier. Wanted to kill you. This world should burn. Burn."
"This world is no different from the one we left." Ryouma said, patting Oryou on the head. She relished the touches. "I mean, assassins got me when I was still alive, right? Those guys will always exist."
"The next time Oryou-san catches one of those bugs alone, I will eat them."
"Well, if they attack first." Sakamoto reasoned. "But let's just settle in for a nice, peaceful vacation, okay?"
"Whatever Ryoma-san says. Onsen?"
"We don't have money."
"Oh, right." Oryou said, sighing. "Who do I eat to get money?"
…
"Why were you so afraid of that woman, darling?"
"Yeah, papa! The black lady was really pretty!"
For a moment, Muzan just stood in front of the house of whomever he had replaced, thinking.
"It just reminded me of something I saw on the mountains one time." Muzan said. "And now it's reminding me to thank the hunter that saved me."
"Hunter?" his supposed wife said, grasping his arm. "But you've never been there-"
"I have to go now. Before I forget." Muzan said, shining a smile back at his family. "It's an old debt."
He took a step forward, before turning back once again.
"From when I was a child."
Piling up the lies, he swiftly left into the night.
"Wait!" his wife said, stretching out her hand. "How would you even know where he was?"
"It was a pity that they had begun to grow suspicious." Muzan thought. "This was a nice coverup family. But now, their patriarch rests within my essence."
Turning a street corner, he turned on his connection to the owner of the infinity castle. A door appeared and opened in the dark streetway as he absent mindedly gave a drop of his blood to a drunk man who just happened to be lying there. As he roared in agony and began to morph and shift, Muzan stepped through.
The castle was as confusing as ever. It resembled a jumbled collection of rooms and what a japanese home should look like, more than actual architecture. All around the place, candles and lanterns stayed lit, illuminating the whole place in a golden glow, even if their flames pointed in different directions.
Muzan, however, was used to the spectacle in front of him. Besides, he had to think about greater matters than a castle layout.
"Call a meeting of the moons. Now." Muzan said to the biwa player that was the owner of the infinity castle. "We have matters to discuss."
"Who should I call, Muzan-sama?" Nakime, the owner of the castle said.
For a moment, Muzan just stood still. Should he really trouble the upper moons for naught but a feeling? There weren't many other mythological beings out there, and even though that woman did smell older and more powerful than anything he'd encountered before… without being a demon.
Was that really possible?
He pondered for a moment. Maybe this was just a waste of resources. With two demons already in town, hunting for the boy with hanafuda earrings, the Hashira would concentrate even more if he sent out upper moons to kill the duo that might not even be a threat.
"Call… Lower Moon Six and Three in. They shouldn't be doing anything." Muzan said.
"Besides, they're all rather weak."
"As you command."
With a musical ting of the four-stringed biwa, the two demons were teleported in.
"Where's Kyogai?" Muzan said, looking down at the two shivering demons.
"S-s-sir…" Lower Moon Six stuttered. "You demoted him."
"Ah, yes." Muzan said, snapping his fingers. "Recently, you all have achieved nothing. Nothing."
The two shivered.
"Master, we have been devouring humans! Hunting down rare bloods! Massacring the demon slayers that are sent to us!"
With a surge of effort, Muzan searched their memories. Certainly, massacring was not the correct word. Instead, it was mostly ambush tactics and using their… rather subpar demon blood arts to destroy individual corps members.
He almost missed Kyogai. At least his demon blood art was sort of interesting. But then again, he did lose his ability to eat most humans, so that was that.
"But no matter. I am giving you both a chance to prove yourself."
"Please order us, Master!" Lower Three immediately cowered and knelt into a kow-tow. Lower Six was a bit late to respond.
"I've only been promoted recently, you know." Lower Six thought. "Why does he expect that-"
Muzan blitzed forward and held his skull in a rather tight grip.
"W-what?"
"I've only been promoted recently, you know." Muzan slowly repeated, his red eyes glinting in malice. "Why does he expect that… what? Finish your thought, Kamanue."
"Sorry, Master!" he yelled. "Please, please have mercy."
"Go slay a man accompanied by another woman that smells like blood." Muzan said. "One wears a white suit, and the woman wears a sailor uniform. Do it quickly. Use the ambush tactics that you like so much. Just… get it done, for once."
"Of course, Master."
…
The two were plopped onto the streets of Tokyo.
"Some other demons that Master has favored are in town too…" Kamanue, Lower Six, said. "Those damn upstarts."
"Some arrow demon and some ball demon." Wakuraba, Lower Three, muttered. "It's not like they're getting threatened daily."
"Shh… don't think those thoughts." Kamanue whispered. "We might still be in range."
Together, the two demons bounded across Tokyo in the depths of night, where they could slowly feel the oppressive weight of somebody peeking into their mind disappear.
"Okay, now we should be safe." Wakuraba said, massaging the annoying X-marks on his face. "Who the hell is that guy, anyways? Does master just want him dead because he looks pretty similar to him?"
"Maybe it's the girl." Kamanue reasoned. "She was probably a demon that broke free of the curse long ago."
The curse, of course, was the restraint on them to never say Muzan's name. The title of Master was very annoying and actually sort of humiliating, but to the person that gave them their second life, if the title of respect Muzan-sama couldn't be spoken, then that substitute would have to be accepted.
"Aren't the ball and arrow demons actually here to hunt another pair? A boy and another demon, or something? Can't master just… kill that demon?"
"Whatever. We're not here to question his decisions" Wakuraba said. "How about we just find the guy, kill him, and then get out of here? To be perfectly honest… I don't like you."
"Well, I don't like you either." Kamanue said. "Stop hogging all of the rare bloods in our area, bastard!"
"Well, if you want them, try and fight me!"
"Oh, yeah? You want to test me?"
"Oi! What are you doing out there? Quiet down, you idiots!" an innkeeper shouted. "What is it with people these days? First, I meet that weird girl and the strange samurai wearing a white suit, and now you… what the hell?"
The innkeeper's eyes met the strange markings and altercations on the two demon's face, and screamed, before shutting the door.
As lights in the inn began to flicker back on with what sounded like flint and steel clicking together, the two demons looked at each other, and grinned.
It turns out that they would be getting information faster than they expected. Even if they abhorred each other due to the constant ranking competitions the lower moons were engaged in, there was one thing that they could unite in.
Slaughter.
…
"Collecting the blood of strong demons is critical to our efforts in turning demons back into humans."
Tanjiro nodded, before thinking back to a time earlier that day.
"Do you know who those strong demons are? I… met Muzan, along with another woman. She smelled… strong. Old, and strong."
"Unfortunately, I left Kibutsuji Muzan's service before the concept of Upper Moons were even a thing." Tamayo said calmly. "Though it is not without reason that we can assume there is at least one strong demon following him at all times, even if it does… go against his personality."
"And by powerful demons, I of course, mean these Upper moons. The ones that can contend with Kibutsuji Muzan's own demonic powers."
Tanjiro gulped nervously. Just standing next to that woman with the soulless eyes had been terrifying. He looked at Nezuko, nuzzling his hand.
If he had to do it to save Nezuko, then of course he would.
"I accept."
Then, of course, the walls began to crumble as a colored ball hit the walls.
…
"Oryou-san senses combat." Oryou said, suddenly looking up from acting as Sakamoto's cushion.
Without money and lodging, they had to live out on the streets. Despite Sakamoto's insistence of not needing to be coddled, Oryou still stretched out her form to keep the ground from coming into contact with Sakamoto.
"It's Japan." Sakamoto said, shrugging. "Somebody will always be fighting somebody. It was like that when I was alive, and apparently it's still like that sixty years later."
"That is not it. Oryou-san senses magic in the air." Oryou said. "People with magic are fighting."
"Well, the holy grail had to come from somewhere, right?" Sakamoto said, grinning weakly. "I mean, mages existed in proper human history. It's not out of the question that they would start dueling now."
"Stop denying the truth. There are bugs around for Oryou-san to eat, and you just want to laze around."
"How about… we just continue to relax today…" Sakamoto reasoned. "And we can find three frogs for you tomorrow?"
"Oryou-san demands four."
Sakamoto chucked. "Alright. I guess that's a deal. But we really do have to get some money…"
…
"You are applying to just be a teacher?" the schoolmaster said. He had only really wanted to see the young man because of his fancy attire, but he turned out to be more articulate than even he was.
"Indeed. I have taught in the past, in the city of Edo, but now I want to experience life in the city of Tokyo."
The schoolmaster nodded to himself. This young man was probably some young noble that had snuck out to definitely "experience life" with his paramour.
"And you bear the name of the great reformer from the Bakumatsu period?"
Sakamoto scratched his head. "My parents were admirers. We weren't really related."
"Oryou-san thinks that you are as great as him." Oryou said proudly.
"He even managed to find somebody with the same name as his wife?" the principal muttered. "I'm actually sort of jealous."
"Oryou-san heard that."
"S-sorry… Well, how does a wage of fifty yen sound?"
"Fifty yen?" Sakamoto went over the rates in his mind. In 1920, it would probably amount to… 50 kilograms of rice? Which would probably be able to pay rent.
"Sure." Sakamoto shrugged. "So, what will I be teaching?"
"What subjects can you teach?" the schoolmaster said. "Clearly, you are educated, but I am not sure as to which you specialize in."
…
"He really can teach every subject." the schoolmaster said, looking at the man teaching through the window.
"Yes. Ryoma is the best." Oryou said.
Sakamoto took a look at the two people very obviously looking in from the window, and grinned. He then looked to the left, and then saw two other young men looking out at him from the brush.
"There must be many people willing to learn, but not able to pay the fee…" Sakamoto thought. "Truly, my reform work is not yet done."
…
"There they are." Wakuraba said, grinning. "We found them. Good job, Lower Six."
"At least we're almost free, Lower Three." the other demon said. "But that woman does look kind of weird. Are you sure she's not a demon? The scent is pretty weird…"
"We demons are the strongest race that walk the world." Wakuraba said, grinning past his X-shaped scars. "We are physically stronger. We can regenerate. We cannot be killed by anything except sunlight and nichirin blades. And as long as they possess none of those, they cannot defeat us."
"So, we strike tonight?"
Wakuraba looked at the patch of sunlight that separated them from the suit-wearing schoolteacher.
"...Yeah." he said. For some reason, he felt a shiver of fear run down his spine as he looked at the patch of sun.
Maybe… demons weren't as invulnerable as he thought they were. The hashira were very, very terrifying.
But what was worse than Muzan-sama's rage, somehow, was looking at the woman that accompanied the schoolteacher. Even if there was no reason for him to be afraid, he still… was.
It didn't matter. He flexed his claws.
Demons would prowl that night, and Tokyo wouldn't know what hit it.
I guess that's a first chapter. Hopefully, I'm not messing up Demon Slayer lore lol.
If you all enjoyed that and want me to continue this, then go ahead and follow/favorite/review. Since one of my other fics is winding down in its conclusion, I'm considering starting a couple other ideas. But there's another Jason (yes, from the argonauts) in KonoSuba crossover fic that I'm also considering writing, so I'm leaving it up to a stats competition.
Discord link: discord . gg / 9t9MK3jHmV
-SpiritOfErebus