THE COLOR OF THE WORLD

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Disclaimer: Kimetsu no Yaiba belongs to Koyoharu Gotouge

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Genre(s): Adventure/ Hurt/Comfort

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Warning(s): Typo is my most loyal fan, spelling mistakes because English is not my mother language, Possibly OOC and a lot of Angst. I hope. Not Beta.

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Manga: Chapter 1

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(A/N): I've been wanting to do this since I saw the mangaka drew the reverse-role AU as their chapter cover. And with the anime now aired, I'm so pumped to create a fanfic for this new fandom!

It'll not be a completely alternate universe tho', just changing the main character's role. I don't think I'm gonna reversed their friends too, I like Zenitsu's personality too much to change it into Inousuke's crazy one. Well...both of them have a crazy personality lol. Besides, Inousuke is too beautiful to have that desperate-pervert personality. If he has to be a pervert, it'll be playboy-smooth talking personality. And I can't picture him as that either hahaha. Hence, no reverse-role for them

I just love the idea of this AU, okay! Another thing I love besides cute boy being badass is a fragile girl being badass! That's the reason why I love Franziska von Karma so much. Besides, Tanjiro's and Nezuko's personality is almost similar—nice, caring, headstrong—so it's easy to swap them around `3`

So yeah. This is not going to be full AU. So if I think the story will not change that much, I'm going to skip it with minimal description and not change the point of view of the characters. Have fun reading

Check my tumblr for the fanart. https(:)/ post/ 184905901714/ kimetsu -no -yaiba -reverse -role -au -because -what

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When happiness ends, there's always...

The fog of blood in the air


"Nezuko!"

She turned to the caller, her black hair with an orange highlight at the bottom that was tightened into a bun swayed lightly. Nezuko, who was on the charge of putting their little brother to sleep, smiled at her brother approaching, giving her a small wave. He's a bit taller than her, burgundy hair and burgundy eyes. A nasty burn on the side of his forehead was spotted, a wound he got from protecting Rokuta after he knocked down the brazier. Wearing a long rectangular earring with a sun symbol on his ears; the only memento he got from their deceased father. Tanjiro looks ready to go to the town, judging from the basket of coal on his back, one of their main income of money. As he arrived, he put his big hand on top of Rokuta's hair, smiling softly, "it's snowing pretty hard right now. So don't wander into the forest too far, okay?"

"I can say the same to you, niichan!" Nezuko giggled, "you know you don't have to push yourself today, right? We can just relaxed and wait until the snow stop."

Tanjirou scratched his nape and chuckling nervously, "Sorry. But I want us to go have a great new year's feast. So I'll sell as much charcoal as I can." He stopped and leaned back, sniffing the air with eyes closed, "I smell the weather changing so give mom my blanket to cover her a bit more. She's a bit stubborn sometimes, I don't want her to fell ill again especially this time of the month"

Nezuko nodded. She trusted her brother when he said something is going to happen based on his nose. Her brother has an uncanny sense of smell, sometimes the townsfolk compare it to an animal, not in a bad way. Nezuko wished she has that skill, it'll help a lot when she accidentally left the food too long and ruined their meal. It happened several times when Tanjiro was away and it was her turn to cook. It kinda miffed her that her cooking was not as delicious as her brother's, but you gotta have a weakness somewhere.

(If only their father is still alive. His sense of smell is just as strong as Tanjiro)

That's fine, though. She may not have a nose of a cat, but she does have other ability that is as baffling as his brother has.

A dark blue fog flew passed her red eyes.

"Ah, I see it too," Nezuko mumbled, "looks like today's weather will be a lot colder this night."

She can see the color of the world.

Every living creature has its own color. She could see them, as a form of a fog that extends toward their body like a string of fate. It's always so amazing, to see ton and ton of colors weaving around like a beautiful rainbow, though it was overwhelming at first when she realized she has this kind of skill. Nezuko was sure Tanjiro experienced this problem when he first got his sense of smell too; overwhelming that he was on the verge of vomiting. Until their father taught him how to control it. And her brother then taught her how to control it too. So she can appreciate the beautiful craftsmanship of life of a living being.

It may not be as instantaneous as his brother's nose yet it brightens her world anyway

(If only she realized that whenever there's a light, a shadow will always lurk within)

"Yea? So please take care of mom if I'm coming home late," Tanjiro grinned as he walked away, "I'll bring you guys some mochi for a snack tonight. Sakura-mochi for you?"

"Uh huh! Thanks a lot, niichan!" she gave him her own grin, "come back home soon okay?"

He raised his hand and gave a small wave without turning his back.

Nezuko, after being surrounded by the other younger siblings asking her to play with them, step into the house. She lay Rokuta on the futon and approached her mother, knitting the unfinished kimono while lightly coughing whenever she stops to take a breath. Nezuko's eyebrows furrowed in worry. Their mother is a seamstress, another job that'll help them to gain money for their daily necessities. However, her mother's health has been going downhill this year, especially this time of the month where snow enveloped the whole mountain they lived in. Nezuko offered to take the job, as it was also her hobby anyway. Watching her hands handle the thread, weaving it into the pretty clothes is calming her being. But of course, as always, her mother refused to.

"Oh no, that's okay. I can finish this on my own," she craned her neck, "where's your brother? Is he already gone?"

"Yes, just now."

"Really. And I want to ask him for delivery too," she rummaged the drawer and pull out five bundles of kimono and yukata, "I've finished them so I want to send it to our customer as soon as I can. Especially one of them asked for a Shiromuku for their wedding a week from now on."

"I can deliver it to them, mom," Nezuko proposed.

"Are you sure?" She asked for confirmation, letting out a small cough that tightened Nezuko's resolve.

"Yup," the girl smiled, reaching out to take the bundle and cradling it in her embrace, "don't worry. I'll try to seek out for niichan so we can go home together."

The worry is still palpable on her pale face as Nezuko changed her kimono into an easy to move yukata. Yet she knew she could not stop her, seeing the fire inside her red eyes, burning like an inferno. She sighed. It's not just the mother, her children are just as stubborn as she was, especially the eldest two. She doesn't let go before she gave her a peck on her cheek, wishing her good luck and be careful.

Nezuko hummed as she trekked down the mountain. It's been a while since she visits the town, she usually restrained herself to help around the house only, taking care of the younger kids to lighten her mother's work when their father has fallen ill and now is long gone. She cannot help but feel excited to see the changes in town, even if it's just small changes. Maybe she could also buy some souvenir for mom and the younger siblings. Tanjirou promised to buy them some snack so she could buy a little trinket if it's not too expensive. A hairclip or maybe socks. Mom said it's okay to use some. It's a new year so they can splurge a little bit. Especially with Tanjiro's word to bring another bundle of coins back. Their brother is true to his promise. When he said he'll sell the charcoal till it left no more, he'll do it. Even if he has to circle the town for a second or third time.

The town was bustling as she remembered. And the townsfolk are just as charming as she remembered too. Some of the snack stores invited her to eat their wares. She accepted one dango and refused the other because she wanted to prepare her tummy for the new year feast. And the mochi that Tanjiro will buy too. That doesn't mean she refused to talk with them, however, especially with how nice they are and how delightful the kids to see her again. So, to her shame, she wasted a lot of time not because she delivered the package to the customer. But conversing with the said customer instead. Before she knew it, it's already night and he hurried her step home.

A shout from somewhere halted her though.

"Nezuko!" a man in her thirty exclaimed from the window, calling her before she could scale the mountain up, "what are you doing, walking around at night? It's dangerous up there!"

"Oh, Saburou-san. It's okay, I can see the color of my family from here," she said. It was not a secret from the townsfolk that Kamado's family—or to be exact, three of the family, one of them already up on the heaven—have their own unique ability, such as Tanjiro. Hers may not be much of a help—in, example, they asked him to search a thief based on the smell that lingering at the plate they broke one time. With Tanjiro's help, the culprit was caught within a day and he gets paid for it. Call it a side job, he said. As long as it's legal, he doesn't mind using his ability to helped people in need—but they have fun in playing 'guess who' with her ability whenever new people come into town and they want to show a little trick, "I can use that as a guide so I will not get lost."

"No. You can stay here, please! Come back!"

"But..."

"It's all right! You're welcome here!" he sounded desperate, face pale and eyes bulging.

"You don't want to run into any demons"

So here she was, in the cozy house of her neighbor. Nezuko ate the dinner the man prepared as she listened to his story. He said he saw Tanjiro just an hour ago, coming home a bit earlier than he expected; sounded like he managed to sell the goods within one trip. He was ready to call him to stay. However, her brother was too quick on his foot that before Saburou knew it, he already blended within the thick forest. He thought it was okay though, as the light still out and he hoped Tanjiro arrived at home before sunset down. But it was not a case for Nezuko, who clearly walking around when the light is already out so Saburou immediately called for her before it was too late. He told her that for ages, man-eating demons have roamed these woods after dark. Even for a paranoid warrior, the beast was dangerous and they can creep up upon their prey without them noticing. Nezuko thought that it was just a myth, something parents tell to scare children so they don't wander around at night without supervision.

"Next time when Tanjiro goes down the mountain, maybe I can ask him to bring us along," she mused as she tightened the blanket around her body and closed her eyes, "There's no need to fear. There's no such thing as demons in the first place anyway."

But now that I think of it...

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Our grandmother said the same thing before she died.


Nezuko bid her goodbye when the morning comes, thanking him for his hospitality and promised to not stay up too late. She hummed along the way, clutching the box that contained a hairpin and pair of socks she promised to buy as a souvenir. Yesterday was a great day. She cannot wait for the feast and have other good memories to remember along the next year.

But she didn't realize.

She stopped short, orbs widened and pupil dilated.

When happiness ends, there's always...

A red fog passed. A lot, and a lot of red fog. It's different from her family red line. It's different from her mom gentle red or her brother's calming red. This one is too red. Too sickly. Too horrifying. Too familiar when her grandma and father took their last breath.

The fog of blood in the air

Nezuko stood frozen as she saw her brother slumped, protecting Rokuta's fragile body with his own bloodied one.

This red fog—

—is the red fog of Death.

"NIICHAN!"

"Niichan! What the—arrgh!" she ran towards the bodies, grasping at his crumpled yukata. She accidentally brushed over Rokuta's skin. Cold. Cold, it's too cold, she jerked her fingers back in horror, "what happ—"

She made a mistake and glanced at the inside of the house, past the ruined, crooked door.

Nezuko could never forget the sight, it literally burned into her mind.

Red, red, red everywhere. How could her favorite color, the color of their family, look so grotesque like this? How could her favorite color, the color of their happy family, look so devastating like this?

Ahh...the corpses. The corpses of her family are the cause of that.

"Mother...Hanako," her lips trembled, "Takeo...Shigeru," her teeth chattering, "niichan...Rokuta..."

What happened?

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"Only niichan body was still warm. Maybe a doctor can save him" she carried him on the cart her brother usually use to pull Hanako and Shigeru whenever they followed him to the city. She tucked his body inside the thick blanket, trying to maintain his body heat as much as possible, "how did this happen? A bear? Maybe a bear too hungry to hibernate?!"

She huffed and puffed, not used to carrying someone who's bigger than her. Especially as her brother's muscle mass weighed the whole cart down, a figure he got after scaling the mountain up and down every day. She almost tripped, but she managed. She will manage. Because her brother's life is on the line here. Her only family alive is on the verge of dying here!

"So hard to breathe!" The snow has been pouring since last night, "The air's so cold, it's freezing my lung!"

Keep going, keep going! Move your feet faster!

Tanjiro's finger twitched—

I won't let you die, niichan! Nezuko will—

A rustle from the forest below. A pair of legs were running between the bushes with top speed—

A tear fell down from her puffy eyes.

The brother stood up from the cart, hands reaching toward his sister's unsuspecting back; Iris and pupil are gone, leaving white sclera enveloping the usual red orbs that now gone, gone, gone

I will save you!

SLAAASSH

BOUM

ROLL, ROLL, WHOMP

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She didn't know what happen. One moment, she was dragging the cart along with her older brother. And the next second, a sharp wind passed on the top of her head—it managed to cut her hair tie and make her hair that was tightened in a bun fell down. Pretty sure it cut some strands like a fine, cutting blade too. But it was a clump of red strands. It's not black. It's not my hair—a big, warm, warm arms wrapped around her shivering body and it pulled. Yanking her away from the dangerous gust and, unfortunately, sending them careening into the forest below. Now, she's on her back, watching the cloud go by. Heart hammering like crazy and sweat after sweat dripped from her forehead like a gushing waterfall.

"The snow...saved me," she coughed, "thank god, the snow saved me..."

But wait. Where's—

"Niichan!" she got up, head swiveling right and left, her breath quickened in panic, "Niichan, where—"

"Is...this your niichan?"

Nezuko gasped, unconsciously step back a little at the harsh tone of a stranger that suddenly reached her hearing. It was a man with black hair, wearing the same, black uniform along with unique haori that was clear it was two cloth stitched into one; the right side is dark red in color while the left side is green and yellow in color, criss-cross in a complex pattern. There's a katana clasped on his right hand. And on the opposite palm is—

"Niichan!" she shouted, took a large step to reach them but the man holds her sword in a warning manner, she stopped. Nezuko saw her brother struggled from the stranger's grips, trying to free himself. Not wanting to worsen the situation, she gulped and said, "y-yes. That's my niichan. He's...he's hurt. I have to bring him to the doctor so plea—"

"He's not hurt," he cut her. Those blank, blank orbs unnerved her to no end and he kept talking, "are you so absentminded you didn't even realize what your brother has become?"

"Wha—"

"Look closely," he snatched Tanjiro's chin and forced him to look upward, "look at him and tell me if he is still your brother."

Nezuko's breath hitched.

Fangs, nerves bunched around his forehead like a crazed beast.

Those warm, warm burgundy eyes that she loved so much turned into dull ginger. Even now as they were talking, the beautiful, burgundy locks started fading, turning into the said reddish brown. She hated it, she hated it, she hated it.

Why? What happened? What happened to her precious older brother that turned him so drastically like thi—

Old man Saburo's word rang through her head.

Demon. Man-eating demon.

But...but niichan has been human. It was only a glimpse of memories, forgotten because she was still a baby. Yet she knew the young face of her brother when he leaned over her. Playing with her, making silly sounds to make her laugh. Niichan has been human, has always been human.

"N-No..."

"Your brother is a demon. Maybe the one who actually killed your family—"

"NO! Don't you dare say that!" Nezuko exclaimed, her heart quickened even more, almost hammering into her ribcage like a festival drum, "Niichan...niichan will never do that! There's no blood on his hands. Or...or mouth! He doesn't kill anyone! He will not kill anyone!"

"Yet you knew he jumped on you."

"No! There's no way that niichan—" Nezuko stopped when she remembered the incident seconds ago, "you...you are the culprit right?" she stammered, "you're the one who cut my hair tie and niichan's hair. You attack us!"

"I'm just trying to kill the demon."

"Yeah, but you're way, way off and that's why niichan tackled me! He was trying to save me from your attack!"

"..."

"Besides...besides I saw it!" she waved her hands in desperation, "I saw another thread hanging around our house."

A black fog so black, Nezuko felt like she was staring right into the abyss

"That thread...that must be the thread from the real culprit! Not niichan!I don't know what's making him act like this, but—"

"That's easy," he interrupted her for the second time, "demon blood got in his wound so he's transformed into a demon."

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She felt her head spin.

Such a thing to happen. While she was safely asleep in town, something horrible happened. Happened to her whole family.

How they must have suffered. And I wasn't there to help them. Wasn't there to save even a single one of them.

Except she did. There's her brother. Demon and growling like a scared creature, but alive nonetheless.

With the sword now pointed at his neck.

"NO! What are you doing?!" Nezuko took another step, not caring with how deadly the stranger's gaze was.

"He's a demon. And I'm a demon slayer. It's my job to banish his kind from this world before he kills another human."

"But I'm...I'm sure there's a way to turn him back. There must be! He never kills anyone so—"

"That doesn't mean anything!" his voice was harsh, it reverberated through the woods, "I can't keep a demon alive based from your word alone. Little did I know, the moment I left you with him, he's too hungry to even recognize you as his sister. Eat you in your sleep and wander into town to eat other unfortunate humans!"

(If only I come half a day sooner, the man thought, if only I was faster. If only I was strong enough—)

"Weakness and empty promises cannot protect your brother or find him a cure" he raised his katana, lips thinned, "and they certainly cannot avenge your family!"

He swung the sword down and—

SHHIINNKKK

—planted it deep into Tanjiro's left shoulder.

"NOOOOO!"

"GRAAAHH!"

Two things happened at a mere second. The girl bellowed and clasped her finger around the rock that buried under the snow, throwing it at him as much as her fragile arm could take. He evaded it easily.

The other one was, the demon brother let out his own set of scream, his body suddenly grew twice a height of a teenager and now was as big as an adult, loosening his grip on the demon's wrist without consent at the same time. The brother squatted a bit lower, turned his body a little to the side before he used his leg to kicked him away. This time, the demon hunter couldn't dodge it with how close they were and could only shift his body a little bit or else that kick will land on his rib and cracked them good.

Then the brother sped up towards the girl.

NO! He skidded to a halt, I'm too far away! He's going to eat her—

Before he scooped the crying little sister in a bridal style and ran to the opposite direction, away from the baffled swordsman.

It was weird, to say the least. A starving demon will kill and eat their own parents and siblings because they need energy. He saw it countless times. That boy is injured, it cost his strength to heal that wound. Not to mention the strength it took to transform into a demon. He must be doubly starved right now. And want to eat human flesh as soon as possible, right there and then even if it just a little bit.

But he ran away from me. Focusing on his sister and brought her away to safety.

No, no way. Maybe the demon just wants to find a hidden place for him to eat the human. No beast will feel safe to consume their meal if a demon hunter was clearly circling them. That must be the real reason why. So, tightening his muscle on his knee, he sped toward them like an eagle spotting their prey. He chased after them, gaze hardened in determination. When he was right behind the demon, sword ready to cut his head off though, the girl popped up from behind the brother's shoulder. With gritted teeth and eyebrows furrowed, she produced another stone and threw it at him, he ducked.

"What the hell is that girl doing!" He growled, "doesn't she realized that her life is in danger?!"

She must have not because at the next second, she threw him another one (where did she get that, really? Has she been accumulating stones when they have their conversation minutes ago? Hiding it inside her yukata without him knowing?). He evaded two of the stones but deflected the third one with his weapon, angled it directly at her brother's ankle.

"GRAAH?!"

"KYAAAH!"

The shock of something sharps knocking the demon off balanced, tumbling them into the snow. They rolled for a whole five seconds, scattering the snow into the air. He thought he heard a loud crack. And judging how the sister's scream cut off, a hidden stone beneath the snow must've hit her head or something and render her unconscious. The swordman hopes it's only a concussion and not a fatal wound.

(Because he already failed. Failed to save her family. There's no way he could've failed to save her life either. The guilt will be overwhelming and he'll regret it for the rest of his life)

They came to a stop as he drew his breath. He stood over them with pity clearly directed toward the sleeping girl. He understands, he did. Her family is dead and his brother has become a demon. Her heart is crushed. He knew her pain, how she must want to cry out and rage at the world for the unfairness of all. I should've killed her brother now before she wakes up, he thought, as he reached for his body and tried to turn him a bit away from the collapsing girl. Strange that the demon curled around her body like a ball, minimizing their impact as much as he could. But why? He understands if he did it just for his safety, but the form he took was clear that he was trying to do the same to the girl.

Like he was trying to prote—

He jumped back when sharp claws swung right in front of his face, grazing his nose a bit and cutting a strand of his hair.

The demon woke up, he cursed. The hunter crouched low and stance ready to unleash one of the skills his mentor taught him but—

"...tect"

He stopped short when he heard the demon growled. Did he just...talk?

"Pro...tect..." the demon hissed, "protect...fa...mily..."

"I...will...pro...tect...Nezuko!"

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The swordsman's eyes widened.

Niichan! Not niichan!

The girl desperate voice echoed like a second sound. As he saw the brother stood in front of the fallen girl, fangs barred and orbs popped. His hands spread to the side, protecting his little sister unconscious form from the befuddled stare of the demon slayer; shielding her from her supposed attacker.

Niichan would never eat anyone!

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Ah...so when I saw her brother running away from him, bringing her along, was true. That it was not my imagination.

The demon made a leap.

He really did try to protect her.

As the demon bounced from tree to tree and ready to tackle him head-on, he sheathed his sword and raised his open palm, intended to chop on his neck and knock him out.

These two may be different.

WHACK


It was dark without light. Nezuko lay in the middle of the darkness, fainted. Her family—mother, Hanako, Takeo, Shigeru, Rokuta—came by and sat beside her, one by one. Their expression was scrunched up, worried with how fragile their robust sister looked. Her mother, her precious, precious mother leaned over her and whispered.

I'm sorry I had to leave you, Nezuko, her voice sounded so sad. Her eyes looked so sad. She smiled, wry and regretful but full of hope, Please take care of your brother for us.

NO! Don't leave me! Her hand reached out. Don't leave me, don't leave me, my dear mother!

GRASP

Her eyes opened.

And realized her fingers (may not be able to grasp her mother's kimono but) managed to curl around her brother's yukata.

Nezuko puffed, tears rolling down from her reddened eyes. Brother is there, unconscious yet alive. She saw the fangs behind Tanjiro's parted lips. Reminding her that yes, it's not a dream. It's not a bad dream. Her family is dead and her only alive brother was turned into a demon. Why? Why why why why—

"You're awake?"

Nezuko flinched as she saw the man from before, the demon slayer, peeked around the tree, watching them with blank eyes. She scrambled up, hugging her brother close and away from the swordsman even though she knew her action was futile. She remembered how fast he moved, even with her brother monstrous strength as he ran away from him minutes ago. She knew he could kill her only family without mercy, without her even knowing. But damn it, she'll try anyway!

The man didn't move, he just kept talking, " do you really want to cure your brother?"

"Wha—" Nezuko gulped when his gaze turned unimpressed. However, her eyebrows furrowed and a metaphorical fire lit behind her burgundy eyes, "yes. If I have to be a demon slayer myself just so I can find a demon and demand them for an answer, so be it. As long as I can turn niichan back to human. And—"

One of his eyebrows lifted as the girl look at her brother's sleeping face, "—and if I can use the same cure to turned other demon back also, I don't mind sharing. They're former humans, right? Just like niichan. They have feelings too..."

The man didn't comment on that one but he indeed continued, "Go see an old man named Sakonji Urokodaki who lives at the foot of mount Sagiri then," he said, "tell him that Tomioka Giyu sent you."

So his name is Tomioka-san...

"Your brother should be fine because the sun isn't out today," he stepped back to the foliage, "but don't let him into direct sunlight. He'll burn. And try to talk to him. He spoke to me before so your theory about him recognizing you may be right. If he cannot talk, however, you should hide those fangs. Don't want people to get alarmed by his oh-so-obvious changes." Before he disappeared entirely, leaving the sibling alone in the woods; tired, confused yet glad that both of them are still alive.

After sitting around doing nothing, trying to regain her sense and bearing, she finally snapped from her stupor. Tanjiro has woken a moment ago when she was still caught up in her own demise, fussing over her like he usually did. If it's not because of his dull, ginger eyes or whine and grunt his throat produced instead of real sentences (he couldn't talk. He couldn't talk, Tomioka-san. Not anymore), Nezuko could pretend that everything is okay. That her brother is still human. That Tanjiro could still bask under the sun and smiled like the said sun itself; so warm and cheerful. No, she reiterated. He could. He could smile. But Nezuko will see that fangs. Will see her failure for not being there and help her family (yet what can I do? I'm not as strong as niichan. I'm not as courageous as niichan. If I'm there, I'm just gonna be a burden and I don't want niichan to pull my weight because of my weakness). Will see the reminder of her broken, broken family.

Tanjiro was flustered when he saw his little sister cried, clinging to him like a lifeline. Mumbling his name and apology, over and over her voice turned hoarse.

Nezuko clasped her hand on the grave they made for their family, praying for their safety to cross over the Tanzu river. Her demon brother—now sporting a bamboo around his mouth—tilted his head, questioning her gesture yet did the same anyway. She kinda wanted to laugh at how innocent he now acted. His hair is also full ginger now, and was cut short because of Giyu's first attack; made him look like Takeo (she mourned for the loss again); it's a bit messy so Nezuko will trim it. After the funeral. After the prayer. After they get away from the open field and find a safe place for Tanjiro to hide.

She tied her hair into one ponytail for easy maneuver, stood up and grasped her brother's rough hand. With a bundle of clothes containing food and money she could find inside their wrecked house, a hatchet as a weapon of some sort, she took one last glance at her family graveyard and mumbled, "let's go, niichan"

And they ran to the horizon, hoping for a new future in this cruel, unforgiving world


(A/N): Nezuko's skill is a common type of synesthesia. Well...not that common because I'm exaggerating her synesthesia by a lot lol.

...actually, if u think about it, canon!Tanjiro sense of smell is a type of synesthesia too. You can see a thread when you smell your enemy? Knowing what the other's true strength or emotion just by smelling them? Yeah, I'm pretty sure that categorized as synesthesia :'D