A young girl with a black haori, a short kimono, and a long socks that it reached above her knees, was running because she smelled blood and she smelled scents of humans so she rushed to them to keep them safe.
She now arrived at a house and saw a man, dead.
I'm too late!
Y/n carried the man in an unbelievable strength and buried him.
I'm sorry, I'm too late. May you rest in peace.
Y/n finished praying and when she turned around, she spotted a box but just ignored it and waited for someone to get out of the mansion.
She stayed because she thinks the box is from someone from the mansion.
A few hours later, she saw a young man and a kid falling from the balcony.
She panicked and rushed to him to carry him and he landed perfectly at Y/n.
The kid jumped down from the young man and looked at Y/n worry.
Y/n looked at the boy and smiled at him warmly.
"Don't worry, sweetheart, he will be alright." Y/n said to the little boy who's sweating all over.
She putted Zenitsu down and let him rest for a bit.
"Does anyone is still there?" Y/n asked the boy.
"Y-yes, it's Tanjiro-san and my other siblings." the boy stuttered.
"Oh, okay then, let's wait for them." Y/n said and smiled.
Time skip by Giyuu is not liked by everyone~
When Y/n was waiting for the other people to come out, she saw Zenitsu waking up and he greeted her with a blush on his face.
And another time skip, Tanjiro and the others went out and a masked boar was fighting Zenitsu because he's protecting the box. While Y/n is asleep.
And that's when Tanjiro came out of the mansion and became angry that he didn't know that Y/n is there.
But Y/n didn't mind anyways, since she's asleep.
"Ahem!" Y/n heard all of the noise and suddenly woke up by clearing her throat.
They heard someone cleared their throat and they saw a woman with a masked on.
"Are you done?" Y/n asked with a smile.
"Um, we're sorry we didn't acknowledged your presence!" Tanjiro apologized.
"No no no! It's fine, really! So, what happened there inside the mansion? Are you guys alright?" Y/n said and looked at the three worriedly.
"No, we're fine! It's just that, this wild boar is bothering us!" Zenitsu shouted at the boar boy.
"HUH?! WHO DO YOU CALL A BOAR, YOU PIG!" the masked boar shouted at him.
"Okay, okay. Allow me to introduce myself. I'm Y/n L/n, I live nearby and I slay demons but I'm not related to the Demon Slaying Corps." Y/n recalled the memories and her eyes turned cold.
"I'm Kamado Tanjiro! This man beside me is Zenitsu Agatsuma and I don't know the name of the boar masked." Tanjiro said with a smile.
"Nice to meet you all!" Y/n exclaimed.
"This might sound rude but can you please take your mask off?" Zenitsu said and chuckled nervously.
"Sure, why not!" Y/n said and took her mask off.
When she took her mask off, they're surprised to see a beautiful woman, standing infront of them.
"Now, I won't wear this mask anymore. I will just keep this in my bag. So by the way, who owns this box?" Y/n smiled.
Tanjiro was the first one to speak, "O-oh! There's a demon in there, and that demon is my sister!" and pointed at the box.
"What?! Your sister?! A demon?! In a box?!" Y/n exclaimed.
"Y-yes, and I hope you won't kill her!" Tanjiro said panickingly.
"Don't worry, I won't. Does she eat humans?" surprisingly, Y/n was now calm.
"No, for the past two years, she didn't eat anyone." Tanjiro said.
"Then that's good!"
"So how about we hurry the bodies now?"
"Okay!"
They all burried the bodies and prayed while Inosuke was shouting at them continuously.
The four, along the Nezuko, are now heading to where they will rest, the Wisteria House.
At the Wisteria House...
"This is it, the Wisteria House." Tanjiro said.
An old lady came to open the door and greeted them.
And then, Zenitsu said the old lady was a monster but old lady ignored it and Tanjiro smacked Zenitsu in the head.
"You may come in." the old lady said and they all came in.
They all came in and changed clothes the old lady provided.
Once again, the old lady prepared them food, Zenitsu said again that the old lady is a monster.
And Tanjiro smacked him again.
And they all began eating...
"So, where are you going to sleep?" Tanjiro asked Y/n and Zenitsu.
"I'll go sleep right where Nezuko is!" Y/n exclaimed excitedly.
"Oh, okay!"
Inosuke, trying to take Tanjiro's attention, he threw a pillow to Zenitsu.
They all lie down, staring at the cealing.
"This bump I got hurt more than the ribs."
"I'm sorry."
"Oi, Inosuke, you should apologize to me! What you did earlier hurts like hell!"
"Nah, I'll pass."
"You should apologize!"
"Fine. If you don't apologize to me, you won't eat with us anymore.".
"Huh?! What do you mean by that?!"
"Do you know, when eating together, the meal will only be more delicious!"
They're now in silent mode.
"Ne, Tanjiro, since no one was asking, I'll ask it myself. Why are you carrying a demon?" Zenitsu asked him.
"Zenitsu, you must new about that box and you still protecting it! You really are a great guy, you know that?" Tanjiro said and Zenitsu blushed.
"You don't have to praise me like that!" Zenitsu said while rolling in his futon while Tanjiro sweat dropped.
"I have keen smell, and I knew it from the start."
"How kind of you, Zenitsu, how strong..."
"No, I'm not strong. Don't give me that. I still haven't forgive you for making Shoichi go home." Zenitsu glared at Tanjiro while he just mumbled nervously.
"Zenitsu, the kid can't protect you. He doesn't have a blade. Moreover, don't rely on a kid. You have the blade, and you should attack for it." Y/n faced them and said while smiling.
"Yeah, Y/n-chan is right." Tanjiro nodded.
Meanwhile, the box was shaking.
"It's coming out, it's coming out!!!" Zenitsu shouted, scared of the moving box.
"It's alright..."
"Woah, Tanjiro! The box is moving! I wonder what your sister looked like!!" Y/n beamed excitedly.
The box's continued to open and the scared Zenitsu he is, he ran to Inosuke who's already sleeping but Inosuke threw him off near the box.
The box's door squeaked and it Zenitsu flinched.
Zenitsu came back to his consciousness and ran to the wardrobe.
That's when Tanjiro called, "Nezuko!" and smiled warmly.
"SHE'S SO CUTE!!!" Y/n shouted excitedly while Nezuko looked at her happily.
Zenitsu on the other side, "Huh...?"
"Zenitsu, this is my-"
"Tanjiro." Zenitsu called him with seriousness in his voice.
"Zenitsu...?"
The two girls ignored them and continued talking happily(of course, Nezuko is just nodding happily and humming happily).
"You...."
Tanjiro looked at him confused.
"You..."
"Just who do you think you are?!"
"Zenitsu?!"
"Traveling with a cute girl like her?! Just who do you think you are?! That's not why I got pummeled and kicked by that wild boar, right?!" Zenitsu shouted.
"Zenitsu, calm down, what happened to you all of a sudden?!"
"DEMON SLAYER CORPS IS NOT SOMETHING YOU'D GO FOR FUN!!!!" Zenitsu continued shouting while Nezuko and Y/n came forward confused.
"GUYS LIKE YOU SHOULD BE PURGED! IMMEDIATELY!"
"Come to think of it, there's a crime for stopping my marriage and a crime for letting Shoichi home." Zenitsu calmed down.
"PURGED IMMEDIATELY!! THE CORPS SHOULD NOT BE UNDERESTIMATED!!" Zenitsu and swing his sword.
___________________________
A few hours later...
Nezuko came out of the box and adjusted her size.
"Nezuko-chan!"
Nezuko looked around and found Zenitsu, swinging like a drunk man.
"Nezuko-chan~!" Zenitsu came to Nezuko who was confused of the situation and started running and Zenitsu came after to chase her.
"Nezuko-chan! Nezu-chan!" Zenitsu continued to chase Nezuko until Tanjiro stopped him.
"Zenitsu, stop chasing her already!" Tanjiro said.
Zenitsu had a dejected face but said, "Tan...Jiro...kun!" he helded Tanjiro's hands and Tanjiro took away his hands from Zenitsu in disgust.
"Tanjiro! Let's be friends!"
"Zenitsu! Please stop chasing us already!"
Tanjiro whined.
Zenitsu continued chasing the duo and that's when Inosuke headbutted Tanjiro in the back.
"ACKK!! Nanda, nanda?!" Tanjiro rubbed his back while Inosuke yelled.
They were all shocked and ran around with Inosuke chasing them.
Huh, what's wrong? Why is it noisy?
Y/n was confused but ignored it and continued getting ready.
A few days later, the three are not fully healed but its enough for them to move in the night.
"Huh, Y/n-chan? You're leaving your things here?" Tanjiro asked.
"Yep! This is where I live!" Y/n smiled
"Really? That's why you changed clothes."
"Yep. So now, let's go onto our next mission!"
(You changed your clothes and this is the images:

Pretend it's short because in my perspective it's short. It's below your knees

This is a Japanese style and I searched it from pinterest. Credits to the owner! With this, you got all of your weapons and your hair in tied in a high messy ponytail. And btw, you don't wear a mask anymore)
"Now, for your-" the old lady said but was interrupted by Inosuke.
"WHAT ARE YOU DOING, YOU OLD HAG?!" he shouted at the old lady.
"Hey! She's just putting something on our backs for our lucky luck!" Zenitsu protected the old lady while Tanjiro held him back.
(Y/N IS FORGOTTEN!! GOMEN'NASAI!!! 😭😭😭)
"Calm down, Inosuke, this old lady right here won't hurt you." Y/n said.
Inosuke calmed down and the old lady began putting the lucky-luck whatsoever.
After that, they thanked the old lady and left to head to their mission in, Mt Natagumo where spider demons live.