"Big Brother." a familiar voice called out, it wasn't Rui, and Tanjiro was certainly glad it wasn't because to be fair he didn't know how much longer he could last hearing those words come out of that annoying stain's mouth.
It was night, so most of the family was out doing whatever they did outside of the house's comfort, but Tanjiro remained behind tonight, he was inspecting his sword which he had been doing from time to time, he didn't have a lot to do these days so he just did whatever would satiate his boredom, "Big Brother…" the voice called out again, Tanjiro decided to give them some attention and turned to face the source with a curious look, it was his 'new' 'younger sister', the one he got along with decently.

It was nights or days like these where Tanjiro got that idea from, that they got along, the younger sister Demon approached him and sat down next to him, glancing at the sword Tanjiro was holding and somewhat cleaning with a cloth, "You used to be a Demon Slayer, didn't you?" she asked, Tanjiro nodded somberly, "I can tell you also don't like the family, but… I see you as a real Big Brother, because you're not like the rest of them… I want to run, but I'm scared they'll catch me and I'll be strung up."

It had been like this a few times, with the younger sister approaching Tanjiro and confessing these things, if he could he'd try to find a way to save her, but he wasn't in any position to do that, he could smell the pain coming from her, and so he'd always comfort her.

Tanjiro held out, from what that Slayer said to him, he really believed Nezuko was alright.
Although, he wasn't sure how much longer he'd handle Rui's punishments, or how much patience Rui had left with him, he felt like the punishments were getting worse, at one point he was even severed in half by one of Rui's threads, sure he won't die of it but it still hurt to be chopped in half like that.

By now he had figured out how the younger brother made those spiders, and it only made the gap between them wider.
He was using some of the bodies Tanjiro's traps had ensnared, initially he thought all of them would just be killed and used as food for the Spider Family, but one night he ran into a convulsing body, he didn't do anything though, he couldn't do much afterall, and then the younger brother confronted him, "Ah, Big Brother!" he said with a cheery grin on his face, "About time you'd witness some of our little pets being born!", something about that sentence was a recipe for rage, but he couldn't act on that anger, he just watched and waited trying to actually see what this supposed 'younger brother' ment with "pets being born", part of him didn't want to know but he'd always been curious, sometimes he hoped he hadn't been so curious.
Like now, the convulsing body suddenly ruptured as hundreds of spiders pooled out, like the body had been used as a spider nest, frankly that's probably what happened, Tanjiro held back his disgust as he knew this 'younger brother' would probably snitch, so Tanjiro just left.
He could hear the 'younger brother' snickering behind him as he did.

He honestly couldn't wait until the family was killed off.

"I'm no good at working hard…" Zenitsu cried to himself as he watched Nezuko improve, "And Inosuke can't bear to do anything slowly.", the two looked frankly horrible.
For about a day now Nezuko had been trying to teach them how it's done, but either she's a terrible teaching figure or the two just can't catch up to her anymore, it bummed the two even more.

That was, until one day, Shinobu decided to intervene with the training, she stood behind Nezuko and placed a firm hand on her shoulder, raising the other as she began to speak, "The technique Nezuko here has mastered is called Total Concentration Breathing - Constant, basically she's doing Total Concentration Breathing all day long, and her condition has skyrocketed because of it! Of course it's a beginner's technique, so everyone can do it. But mastering it takes serious effort!", she had begun to walk over to Inosuke mid-explaining and now placed a firm hand on his shoulder, "Anyways, of course you can do it… But if you can't then that's that. It'd be a shame though." she said, and Inosuke immediately caught the bait, "HUUUH!? IF IT'S POSSIBLE THEN OF COURSE I'LL DO IT! DON'T TALK ME DOWN! I'LL MESS YOU UP!"

He's really worked up now.

Shinobu soon went over to Zenitsu, clasping one of his hands in her own, "Good luck Zenitsu!" she began, "I'll be your biggest cheerleader!", and of course he took the bait too.

From there on forth, it only took them nine days to master Total Concentration Breathing - Constant, needless to say all three were cheering each other's victories and it was revealed that Nezuko was indeed a terrible teacher.

. . .

"Inosuke! Zenitsu!" Nezuko began, barging into the duo training on their own, "I hear that my reforged Nichirin Sword is coming today!" she said happily, gaining some serious curiosity from the upside-down Inosuke doing a handstand on a broom, "Really!?" he cried out, "Yeah! I heard from a crow!" Nezuko replied, soon after the duo hurried to the gate of the Butterfly Estate, "Mr. Haganezuka!" she screamed out after exiting the gates, looking on as two swordsmiths approached the gate, they seemed to be talking to each other as Haganezuka handed his hat over to the other and began sprinting over to Nezuko, "It's been so long!" she said happily, "Have you been…" and then she realized he was holding something, and looked like he was ready to stab, "...Well…?"

Indeed, the man was holding a knife and had just attempted to stab the young girl who luckily jumped aside at the right moment to not get a chest full of knife.
"W-Why…?" she stammered as she looked at the masked madman, who had turned to face her by now, "I can't believe you broke my sword! I can't believe it!" he said furiously

"I'm Sorry! But I almost died! My opponent was really strong-!", Nezuko's sentence was cut short as she was violently poked in the cheek several times, "Excuses!" Haganezuka began, "I don't need your excuses! My sword broke because you handled it wrong! How else could it snap!? I'm going to kill you!"

Reminder that this man is 37 years old.

So for about an hour, Haganezuka chased the terrified Nezuko around while violently swinging his knife about.

I took the help of Zenitsu, Inosuke, and Shinobu to get him to calm down, and once calmed down they were finally ushered inside to present their swords.
"Well, Haganezuka's love for his craft is greater than anything else, he's very passionate about his work as you can see. Oh, I'm Kanamori, I forged the swords for Inosuke.", the other Swordsmith said as Inosuke sat outside eyeing his new blades, "If they serve you well in battle, I'll be happy.", "That's good, his swords were terribly chipped." Nezuko said, trying to ignore the pain of being repeatedly pummeled on her back by Haganezuka.

"Ah, they're so pretty. The blue-grey has a faint shine, an elegant color that befits a Katana. How do they feel in your hands? It's my first time making swords for a dual-wielder.", Inosuke didn't answer, merely got up and walked over to the nearby pond, he began selecting rocks for… something as the group watched on, eventually he found one he seemed to like and… began to chip away at the swords…
Needless to say, everyone was speechless as Inosuke defiled the blades, turning them into jagged monsters, "That's better." he said.
"I'M GOING TO KILL YOU! YOU THANKLESS BRAT!" Kanamori screamed as he tried to reach for the boy, being held back by Nezuko.
Inosuke didn't bother, and began to chip the second blade, "THAT'S IT! YOU'RE A DEAD MAN!" Kanamori screeched out.

It took them even more manpower to calm him down.

Eventually, once he did calm down the two swordsmiths left, Kanamori completely ticked to beyond human limits, with Haganezuka kind of… impressed.

. . .

At the end of the day someone else had arrived, Nezuko barely recognized the man but once she saw his unmistakable Haori something lit up inside of her, it was the same person that had sent her on her path, "Tomioka!" she said happily mid-routine, causing her to hitch and painfully fall off the wall she was running on top of, Giyu just watched as she had fallen down and got up, walking over to him with a bright smile, "...I'm sorry, I don't recognize you." he said.

Initially Nezuko was taken aback, but then she remembered she probably looked very different from that fateful day, so she flared up again, "I'm that girl from uhhhh… I think two years ago, right? The one with the Demon brother!"

It was Giyu's turn to think, before something seemed to click, "Oh, right, you're that girl I sent to Urokodaki."

"Yeah! ...Anyways, what brings you here?"

"Kocho wanted to gather some people."

"Oh!"

. . .

Indeed, she had been gathering a few people, most of which were now enjoying some tea and chatting amongst each other, Giyu still had that aloof expression and was mostly silently, just occasionally answering a minor question, and everyone quieted down when Shinobu herself entered the room, "Ah! Tomioka-san! Good to see you." she said, "I'm sure you know why you're here, right?"

"No, I'm not sure."

"I see you haven't changed a single bit. Well Tomioka, today a very important message will arrive. So I needed you here." Kocho responded, and as if on cue a Kasugai Crow had landed down outside and hopped over to the group of Slayers, before it spoke, "Caw! I'm glad to see you're all here! Oyakata-sama will be glad. Rest up good! In two days is the night of the raid, thanks to a certain girl among us it has been revealed a member of the Twelve Kizuki has been making Natagumo Mountain their home, therefor with the help of the Hashira you will raid the mountain and eradicate the Demons, aswell as the member of the Twelve Kizuki!"

Soon would come the fateful night, Nezuko would be reunited with Tanjiro.

Tanjiro clearly remembered his encounter with the Father Demon, but said Demon either didn't care anymore or just didn't recognize Tanjiro, the Father was surprisingly… obedient?
Tanjiro remembered one time when he ran into the Father Demon, it was an odd experience.

. . .

"Let's see… My threads aren't exactly good for cutting, they're sturdy sure but I can't really level a tree like Rui. I have nets, which probably speaks volumes about what they're meant for... ", he'd been thinking like that for a while, the idea of returning to the Demon Slayers had crossed his mind quite a few times and he'd usually ponder about what would be changed, today specifically he was thinking about what he could use his threads for during combat.
His little alone-time had suddenly been interrupted by rustling behind him, he turned to face the source and the Father walked out a few moments later, approaching Tanjiro.
He didn't know how to respond and before he knew it the Father was looming over him, realization struck Tanjiro as he was wearing his Haori tonight which the Father probably remembered, fear entered him for a moment before the Father just, spoke.
"Son." he said with a much calmer version of that ruthless voice he'd been using to tell him to 'stay away from his family' that time, and then he ruffled Tanjiro's head, it was firm and Tanjiro wasn't sure how to respond as the Father sat down next to him, taking a pebble and skipping it across the water before handing Tanjiro a pebble, probably to try the same.
It went back and forth like that, almost like a competition, if Tanjiro didn't feel so awkward sitting next to the pretend father he'd probably actually see him as a father figure by now, they skipped rocks for about half an hour before the father stood up, ruffled Tanjiro's hair again, and left.
Tanjiro… was unsure of how to feel.

Needless to say Nezuko barely got any sleep that night, next night they'd go out and raid Natagumo Mountain properly, Kocho and Tomioka would join them and then split off, the Kasugai Crows would keep a close eye on the situations and notify everyone if the Twelve Kizuki member had been located so that the Hashira could converge upon them.

But Nezuko wasn't thinking about that, she was thinking about Tanjiro, what he could possibly be going through right now, the possible agony he'd be enduring this exact moment made Nezuko's heart sink, and it only got worse when she'd think of the possibility that Tanjiro would have already been strung up and burned away at dawn, or that one of the Hashira didn't recognize him and decapitate him pretty much instantly.

She really wasn't having a very good time.

"Hrrgg! Why does it have to take so long!?" she cried as she angrily rolled around in her bed, "At this rate Onii-chan will be dead already by the time I get there.", she hated her flaring imagination at times like these, how she'd imagine her brother's possible deaths, or agony, it made her uneasy, and now that the coming raid was drawing near those images only grew stronger, she'd find out her brother's fate during the raid, no earlier, and it made her incredibly impatient.
Perhaps he had already consumed Human Flesh at this point, she'd figure the family would force him to eat, she'd probably have to end her journey because of that, what if Tanjiro had become a bloodthirsty monster by now that just wanted to feed like all other Demons, one she'd have to kill.

. . .

Past the night and day, the raid had begun.
Nezuko was one of the first to discover an enemy, blade shining in the moonlight and blood dripping from his mouth, as she engaged the Demon gave off a familiar vibe, but Nezuko wanted to find her brother.
That's all that mattered, so she overpowered the bladework of the Demon and decapitated him.

"...Sorry." she heard from behind, turning back there laid Tanjiro, turning to dust as he smiled at her.

. . .

Nezuko woke up with a scream, another nightmare.
She had fallen asleep three times tonight, each time she'd have that kind of nightmare, she couldn't set her mind straight as her imagination ran wild with possibilities.
She just wanted to get the raid over with.
She wanted to be with Onii-chan.