Summary: Nezuko knew she shouldn't have gone down the mountain. She knew she shouldn't have left them in her bout of selfishness. Now, she has to take care of her turned brother, and fight demons whilst searching for a cure. As well as fending off her clueless brother's suitors, apparently. Really, what's a girl gotta do?

Warnings: Role-Reversal!AU, Yaoi, Slash, Possible!Yuri, Muzan Being Muzan, Zenitsu Himself, Inosuke Being Inosuke, etc.

Disclaimer: If I owned Kimetsu no Yaiba, it would star Tanjiro and his Harem, okay?

Nii-chan was always their pillar of hope. Their rock, their refuge, their sanctuary.

He was always there to lend a helping hand, even to strangers. It was how he endeared himself to the villagers at the foot of the mountain. Nii-chan was absurdly kind, ready to patch up a wound or cook for a lost traveler, adamant in making them all eat before he would, staying up late in night and waking up early in the morning to sell charcoal or whatever wild animal he'd hunted and skinned.

Nii-chan was the best. Nii-chan was like a kami to them.

Burgundy locks and eyes that seemed like rubies underneath the sunlight. He was ethereal, majestic.

He was Kamado Tanjiro. He was Nezuko's Nii-chan.

Even if he was now a demon, he was still the same Nii-chan that fussed over them all, scolding them and singing them lullabies to sleep.

She knew. She could see it in his eyes. Nevermind the slits, nevermind the flecks of gold that appeared every now and then.

He was still her Nii-chan, and this time...

This time, she would be the one he would depend on.

—

"Nii-chan! Look what I—Nii-chan?"

Nezuko furrowed her eyebrows, wondering where her turned brother went this time. Ever since turning into a demon, her usually calm Nii-chan had become surprisingly michievous, leaving at random hours in the night only to return when the signs of dawn were approaching, making Nezuko worry sick and angry.

(She wondered if this was his way of reliving his childhood. One that was cut so early when their dearest father died)

Suddenly, a familiar mop of burgundy hair popped out of the hole she hadn't noticed, and she giggled at the sulking form of her brother.

Ah, he missed the sunlight. It was a shame demons would burn underneath the rays of the sun.

"Come here, Nii-chan. Look what I made!" She then proudly presented her work, a basket weaved from bamboo strips, and smiled when she saw Tanjiro nitpicking on some of the loose weaving she had done in a hurry. Nii-chan was always the better one in handicrafts and repairs. He was almost perfect, the ideal husband and wife all rolled in one. Though, he was a bit of a workaholic, and stubborn to boot.

"This way, I can travel with you easily! Also, remember that one time you turned big when Tomioka-san tried to attack you?" Tanjiro nodded, still looking a tad guilty about slapping the swordsman away in a fit of fury. Nezuko personally thought he deserved it, but of course, her brother's bleeding heart would always shine through. "Can you try becoming smaller, then? You know," she mimicked turning into a small ball, knees hugged against her chest. "Smaaaall."

Tanjiro tilted his head, before stepping inside the basket and shrinking. He looked adorable, and definitely huggable. Nezuko had to resist the urge to scoop him up and never let go. They can do that later when they've covered enough ground.

They were making good progress when they've come upon a demon feasting in a temple.

Nezuko saw red.

—

"You hesitate for too long, yet your anger clouds your vision and clear sight."

Nezuko stared uncomprehendingly at the tengu mask glaring down at her battered form. He had introduced himself as the Urokodaki that Tomioka-san wanted her to find. But what was he doing here, instead of being in Mount Sagiri?

His blue, cloud-patterned haori shifted slightly as he turned to face her brother, who had his palms together as if in prayer, chin tucked in and murmuring something vaguely familiar.

"Your brother..." he started, and Nezuko shifted her stance. If he was going to kill him like Tomioka-san initially wanted to do— "...is a unique case, for a demon."

... What?

Urokodaki glanced at her and her position, before shaking his head. "No harm will befall your brother as long as I am here. He has a kindness no demon or human could have. Yet here he is, with a soul so pure it shoudl have purged the demon within him." He sighed, then, almost sadly. Heavily, as if he was tired and so, so old. "Come, and follow me. Bring your brother as wel."

"If you can catch up, that is."

—

The impromptu race was not appreciated by Nezuko's legs.

She had just come out from a nasty battle with a demon, and her brother wasn't exactly light to just lug around. Meanwhile, Urokodaki was still merrily making his way five times faster than Nezuko with nary a care for the world and the steadly uneven road. Honestly, how old was that man even?

Finally, they reached a small house, and saw a figure waiting for them there.

It was a little girl, looking as if she was merely a year younger than Nezuko herself. She wore a short, flowery yukata and had a fox mask with flowers painted on its cheek. Her short, spiky hair swept outwards, and her eyes had a kindly sheen on them much like her Nii-chan had.

"Okaeri, Urokodaki-san," she greeted happily, all but beaming at the old man who patted her head. She turned her sky blue eyes towards a panting Nezuko, and smiled. "Hello, stranger-san. And who might you be?"

Nezuko flushed at being seen in such an unsightly way, but pushed her embarassment away to greet the child. "Kamado Nezuko. Tomioka-san sent me here. And you are?"

The little girl grinned. "My name's Mamoko! Nice to meet you, Nezuko-nee!"

("Nee-chan, Nee-chan! Let's play, let's play!")

Something in her heart clenched painfully at the sound of young, hopeful voices calling out for her, and she hoped Makomo didn't notice the tears gathering in her eyes.

Judging by the worried frown on the youth's face, she pretty much failed in hiding her sadness.

Thankfully, before Makomo could ask what was wrong, another person came from the mountains.

It was a very, very familiar person.

"Ah!" Nezuko exclaimed, fatigue and gloominess gone. She pointed a finger at the newcomer (Nii-chan would admonish her if he ever knew), and blurted out: "Momo-san!"

'Momo-san' looked at her blankly. "Pardon?"

—

Nezuko remembered Momo-san. She remembered how his eyes widened in awe and wonder when he saw her Nii-chan smile at him so sincerely.

How could she forget the first boy whom had fallen for Tanjiro?

It was autumn, that time. The leaves were falling like shades of colors from the sky, and the mountain looked as if it was a whole new world.

Nezuko loved autumn, just as her brother loved spring. It signifed beauty before and after death, a new beginning and end.

She was down in the village with her Nii-chan for once, accompanying him as he pulled the cart filled with charcoal and some of the fabric Nezuko helped their kaa-san knit. It was good business during this time of the year, since the air was getting chiller and the nights were becoming colder.

They met Momo-san when some thieves tried to steal their hard-earned money, and Nii-chan (sweet, kind Nii-chan) was hestitating in unsheathing his hatchet when a sudden blur came and took them all down.

"Are you a man? How could you just stand there twiddling your thumbs when these small fry were this close to robbing both of you blind!"

Momo-san still looked the same as then, with peach hair borderlining on pink, a fox mask with a scar similar to the one on his face, a green-and-yellow haori and a katana tied on his waist.

"Thank you!" Nii-chan said, eyes shining and cheeks flushing in happiness.

Nezuko saw the moment Nii-chan captured his heart, saw the dilating pupils and gaping mouth Momo-san sported.

They tried to invite him over for dinner as thanks, but—much to Tanjiro's confusion and Nezuko's amusement—he had denied the invitation vehemently whilst sputtering underneath Tanjiro's worried and downtrodden gaze.

"M-Maybe next time, alright?" He muttered, and turned beet red upon becoming victim to another one of Nii-chan's shining smiles. He put the sun to shame whenever he was happy, really. It was something that made everyone feel at ease whenever he was around.

"I'll hold you onto that, then, Momo-san."

Momo-san opened his mouth to speak, maybe to correct him and tell them his real name, but he stopped and instead nodded, flashing them a slight smile and wave goodbye as he left.

—

"It's Sabito, not Momo, Nezuko-san."

They were now inside Urokodaki's house sitting in the living room-slash-dining-and-kitchen, circling a pot filled with boiling stew as Urokodaki poked it every now and then.

Nezuko laughed. "Of course, Mo—Sabito-san. Me and Nii-chan were always waiting for your return, you know. Nii-chan was wondering what food he'd make if ever you were to come back."

Nezuko smirked slyly, mentally cackling as she got her desired reaction. A pink tint dusted the composed teen's cheeks, and she could practically feel the eyebrow Urokodaki raised as well as Mamoko's curiosity.

"Speaking of your—" here, he cleared his throat. Nezuko struggled not to guffaw. That would be rude. "—brother, where is he? He doesn't seem to be the type to let you wander around all alone."

Nezuko sobered up at that, and the other two noticed the shift in the atmosphere. Sabito inhaled sharply.

"Is he—?"

"No," Nezuko shook her head. "But... it'll be better if I showed you."

Walking towards the baskte she had woven, she unraveled the cloth added as an extra precaution and waited, sitting in front of it.

"Nii-chan? Guess who I found in Urokodaki-san's place."

Sabito and Makomo stared, wide-eyed, as Tanjiro popped out of the basket he possibly could not have fit into, his bamboo mouthpiece hanging around his neck as he looked around his new surroundings.

When his eyes landed on Sabito, he smiled.

Sabito felt his face heat up.

"Y-Your hair grew," he pointed out dumbly. Nezuko giggled behind her hand. Indeed, her Nii-chan's ponytail had reached below his waist now. And Nezuko was hardpressed to cut it. It was unfairly beautiful, and it's wild look suited Tanjiro, however strange that seemed.

"He became a demon when I was delivering an order down the mountain."

Sabito froze, and looked at where Tanjiro was patting his head. Shockingly enough, he didn't feel any malice or threat from the burgundy-haired boy. He still felt the same as when they last met: safeprotectionfireflamesembersneverendingpeaceandcalm.

"Is that so?" he replied, daring to run a hand through Tanjiro's locks. Tanjiro merely blinked, before his eyes curved happily. He likes it, apparently.

(Nezuko was struggling not to burst out in laughter. Urokodaki's mask finally exuded realization)

—

Training with Urokodaki was harsh, almost hellish, even.

Going down the mountain was easy. But going down the mountain with increasingly harder obstacles was a pain and a half.

Nezuko would always come home bruised and injured, which nearly made her brother cry and rip Urokodaki a new one. Though he calmed down when Sabito and Makomo explained the situation, and Tanjiro decided to train as well with Sabito. Said scarred teen was more than happy to oblige, and was running the demon ragged with his training regime and katas.

Bit by bit, month after month, Nezuko could feel herself grow stronger and faster. She could feel the muscles becoming more pronounced, could see the growth in her body as well as in her attacks.

Mamoko had decided to help her out, since they were both speed and agility to make up for their lack of strength. True, Nezuko was stronger than the average woman, but she still had to compensate for it and compensate she did.

Her Nii-chan was working harder than ever. It was something he excelled at, and made Sabito fall harder for him in every way. It always made Nezuko giggle whenever she saw the utterly besotted look Sabito had during the times Tanjiro wasnt't looking. It was both funny and sad. Funny, because Sabito was a calm and steady-headed man. Sad, because Nii-chan was denser than a rock and would probably never think of love as soon as Nezuko lived.

Ah, the woes of falling for an older brother.

Then a year passed, and Nezuko's final test started with this one sentence:

"I have nothing more to teach you."

—

A boulder. She had to slice a boulder in half.

What the hell, Urokodaki-san?

"He's not kidding, you know," Sabito said, from where he was sitting near a tree. Makomo was on a branch, swinging her legs to and fro. Nii-chan was making flower crowns, and had already finished one. It was sitting proudly on Sabito's head.

"Were you also required to do this?"

At Sabito's nod, Nezuko groaned.

"And I succeded."

"Me, too," Makomo chirped.

Nezuko very carefully did not bang her head on the boulder.

—

It took weeks before she got the Total Concentration Breathing down. On another note, her brother had already gotten it at least a month before her!

(Her Nii-chan is awesome that way)

So, in this fic, since Sabito beloved went to Tanjiro's village, he wasn't able to go to that year's Final Selection, hence saving him from his death. Also, SabiJiro anyone?

I'm still not sure whether I should ship Tanjiro with one person, or make it a threesome. Or foursome, starring Giyu, Sabito and Rengoku. Maybe add a bit of Muzan, too. Idk.