Author note:

This is my first demon slayer fanfic.

Now if you don't like stuff of people traveling between different worlds of the fandoms that I like since I do it similar to kingdom hearts do, then don't read! I won't be writing this fanfic all the time since I only have the first two volumes of the manga of kimestu no yaiba.

There are more notes within this and at the end.

Kairi Redfield was panting, not looking back as she used shadow travel (an ability she rarely uses) to get to another world far away from the abusive magical world and the betrayal she was feeling.

She sat down, her back against the tree, she couldn't believe it, not only did she have to deal with Dumbledore and Fudge's bullshit and obsessed with trying to control her, but now her own godfather wants to control her.

It was times like this…it made her wish more than anything that she could kill herself, just to end everything.

But she can't, she didn't survive through so much just to give up at a later date.

Kairi's eyes snapped up to see a boy with reddish hair and eyes, wearing a patten haori, a blue scarf was wrapped around his neck and there was a big basket behind him.

"Konnichiwa, I'm Kamado Tanjiro." the boy said in a gentle tone, "What's your name?"

Kairi sniffled, "Redfield Kairi."

Kairi was very aware of Japanese culture since Angeal and Sephiroth drilled it into her head along with its language.

Besides JApanese was her favorite language and she doesn't even understand why back then or now. It…just seems to have some comforting feeling to it.

"Kairi….are you all right?"

Kairi sniffled, "Not really."

"Why don't you come with me? Me and my family would be happy to have you for the night or a few days."

Kairi thought about it, her body was aching and very cold. The air was very thin from where she sat. "I suppose."

"Great, Kairi-san!"

"I'm 15?" she asked, knowing she was slightly older than this kid.

The boy looked a little embarrassed, "Kairi-Obaa-san!"

Kairi couldn't help but smile, shaking her head. She slowly got to her feet and followed the boy to where his family was supposed to be. But then a rough man's voice stopped them and both of them turned around to see an old man through an opened window.

"Hey, Tanjiro-kun!" The older man shouted out, "you aren't….going back up the mountain, are you!?"

Kairi looked at the man to see worry and concern, it isn't that late…is it? But the older man did look a little scared for Tanjiro, that she could tell and sense from him.

"It's too dangerous!"

Maybe the man was worried about some animals that don't hibernate during the winter and might attack them? Kairi thought to herself. Possibly.

"I've got a good nose for trouble, we'll be fine." Tanjiro told the older man.

Kairi wondered if he was a mutant or if it was just a strange ability. But then it was like how she can see people\s auras.

It was one of the reasons she had been nervous about her adoptive father, Billy Anderson when she first met him. His aura had been so black, like black smoke and it had frightened her.

She took a steady breath in to avoid her flashbacks with him.

Billy had hurt her so bad that sometimes she still can feel his belt hitting her back or whip (depended on how much he drank, but if he drank a lot more during the day it would be the whip), sometimes she feels how brutal the rapes were or sometimes it was other things that she didn't like to think about.

But then came hogwarts…in a way, she had to thank Billy for abusing her so bad because she was horribly bullied by Lavender Brown, who would use a hair straightener against her arm, calling her, "My hair straightener checker" hell…she still had the burns marks on her arms, one of the reasons she wears hoodies or long sleeve shirts to hide them from people.

Then there was the incident at Hogwarts, she had fallen asleep at the library studying for the exams. But when she went down some moving stairs, she felt someone's hand push her and she fell from a height that nearly killed her but…Kairi just wished she knew who would try to kill her for whatever reason.

So in a way, Billy prepared her in his own sick way.

Kairi shook her head, paying attention to what the man was saying now, "You don't want to run into any demons."

Kairi's eyes widened, demons? Not friggering again. Between Annabelle and the demons that herself, Dean and Sam Winchester had to deal with, she was getting fed up with having to deal with demons.

So they went into the man's home, Kairi took her trainers and socks off. But for some reason, it felt normal to her.

She sat down next to Tanjiro, she picked up the chopsticks, picked up the bowl and started to eat but then the older man began to talk again.

"For ages…man-eating demons have roamed these woods after dark. So you two shouldn't walk around at night. Eat, then sleep. You can get up and go home early tomorrow."

Kairi just blinked her eyes at his explanation of demons.

Man-eating demons? She's never heard that one before. The demons that she had dealt with usually wanted to possess her or suck out her soul.

Now there's man-eating ones? Maybe the man was talking about vampires or zombies?

But Kairi couldn't bring herself to ask.

They finished eating, the man laid out futons for them. Just before Kairi laid down, she removed her hoodie and pulled her ponytail out, letting her dark hair with yellow and red stripes.

It's something that made her curious as a child, but now she knows since her father, Chris told her after they were reunited a few years ago.

Her father had been a little too adventurous and somehow he got pregnant with her.

She doesn't have one dads, but two. He told her she had a Japanese father he had helped out once. But he didn't often talk of him, so she figured….it was too painful for him.

Kind of like Tadashi, her first love.

"But..can't the demons come inside houses?" Tanjiro asked him.

Kairi looked at the older man, "yes, they can."

"But…then..why don't they eat every one?" Tanjiro asked.

"Because demon slayers cut them down."

Kairi's eyes widened but she rolled onto her side, trying to think about the info she just received. So were demon slayers like hunters but only for demons?

She figured she'll get more answers eventually. With that thought she fell into a deep sleep.

For once she slept through the night for the first time through the last few years. Usually she wakes up from her flashbacks of the baker's house, the village or from when Joel was killed.

The following morning, they were ready to leave but as Kairi tried to put her hair up, her hair bobble snapped in tow, which made her sigh since it was her last one and it had held on for a very long time until now.

The older man came with her with a sky blue ribbon, she gave him a bow and said, "arigato."

Kairi pulled her hair back up and tied it back with the ribbon. She then followed Tanjiro back up the mountain, the air was a lot easier for her now. Maybe she found the air last night difficult to breathe in because she was scared.

Kairi saw Tanjiro stop walking so she catched up to him to see a shock expression on his face.

"Tanjiro-san?" she asked.

Her new friend didn't say anything so she looked at what he was seeing and she saw a woman laying on the snowy ground, her hand covering a child, but even Kairi could recognize the blood that covered the snow.

What had happened? An animal attack? These man-eating demons? Or some sick psycho that came through?

Kairi watched as Tanjiro ran to his family.

"What hap-what happened!?" he asked the girl and the kid on the ground, "What the..? Agh!"

That made Kairi run to him as he looked into the japanese house, she looked to find blood covering the house and her eyes widened at his dead family, she could not see their aura's nor sense their life force.

"Mother…Hanako…Takeo…Shigeru….Nezuko…Rokuta."

Kaiir did sense, however, one life force, it was faint but it was there. She looked down at the girl in the pink kimono. "She's still alive."

"wha?..Nezuko."

Kairi helped him get her onto his back and they both ran down the mountain, trying to get back to town. But it had taken them ages to get up the hill. So how were they going to make sure that Nezuko-san was going to make it?

Kairi just prayed.

Suddenly there were sounds from Nezuko that made sounds that were similar to Kairi a little too damn well. When she looked, she saw Tanjiro fall along with his sister.

Kairi found her way down and went to Tanjiro.

"Tanjiro-kun, are you alright?" she asked, helping him to his feet.

Kairi heard a slight growling, so she looked to see Nezuko standing with her head down. Kairi wasn't sure what to make of it, Nezuko shouldn't even be standing…

So how is she doing it?

"Nezuko!" shouted Tanjiro, "Are you all right?"

Kairi wanted to stop him, but a chill made her freeze. Something just wasn't right. All she could do was watch helplessly as her body couldn't move due to the cold and the effects of the cruciatus curse.

Basically her body was still exhausted, having just a few hours of sleep and a small bowl of rice wasn't enough. It was a wonder how she was still standing on her two feet.

Suddenly, Nezuko's head snapped up and started to attack Tanjiro, Kairi tried so hard to snap her body out of its shock and go to help her friend. By the time she got there Nezuko was already on top of him and the only thing that was holding her back was the stick that was between her teeth.

Was this what that older man was saying earlier about man eating demons?

It was more like they were zombies, are all man eating demons like this? Or is it just newborns?

Kairi put her hands onto Nezuko's shoulders, trying to pull the girl away from Tanjiro.

"Hold on, Nezuko! Fight it! Fight for your life!" Tanjiro shouted out to his sister, "Be strong, don't become a demon! You can do it!"

Kairi then saw as she tried to pull a bigger NEzuko away that she was starting to cry.

Is it…..Does Nezuko have some humanity within her?

But then Kairi heard a whooshing sound behind her, as if someone was flying or jumping through the air. She looked behind her to see a man with a ponytail and a mismatched haori.

Nezuko grabbed her by her hoodie and jumped.

Did she just basically save them?

The man looked at them with no emotion, but she did notice his surprise at her though.

But why?

"Why do you protect her?" he asked in a deep voice.

"S-sister! She's my little sister!" Tanjiro shouted out.

He then looked at her. "Who…are your parents, your family?"

Kairi bit her lip, basically no one is supposed to know about other worlds. The only reason she knew about them is due to traveling to different worlds and dimensions due to escaping people that had abused her since she was 4 years old.

Plus? She didn't want her dad, Chris, getting hurt.

But he understood how she wants a permitted home where she can be loved and for once in her life, be safe from those who abused her.

"C-Chris Redfield is my mom-dad, he gave birth to me." she said in a whisper. "I don't know my bio chichioya." she said, looking down.

Besides…he probably wouldn't want her once he finds out how much of a burden she really is. If anything he'd probably just send her away.

"Your hair…" the man with the kanata said.

Kairi is aware that the bottom of her black hair has yellow and red, it made it look like her hair was in flames. Ever since it just mysteriously appeared there, Kairi really liked the hair color.

The only thing she hated about it is that it made her stand out.

"What about it?"

"It reminds…." the man shook his head and looked back at Tanjiro, "That is your little sister?"

But Nezuko just tries to escape from Tanjiro's hold, growing at the man that stands before him. The man suddenly dashed before them and Tanjiro went over to his sister…..

Author's note:Now we'll be switching to Giyu's pov. I'll be doing this occasionally if it fits within the story of Kairi's journey. But it won't be all the time.

Tomioka Giyu grabbed the demon that used to be the boy's sister, going past the shaking girl in front of him.

To be honest…the girl with the black hair with the flame-like ends surprised him, judging by her clothes it was obvious that she was not from this world.

But her hair was black with yellow and red at the bottom of it, it was tied back into a ponytail. Her eyes were blue with orange sparks.

However she was quite thin and small, it made him wonder what her age was. But her eyes….they were very sad, frightened, which could be understandable if she hasn't seen a demon before. But….

He could tell that she had been through something traumatic judging how she held herself, her shoulders were tense and there was a hardness in her eyes with no trust in them.

What had that kid seen?

"Nezuko!" shouted the other kid.

Both of the kids moved towards him, so he gave them a glare. The girl was smart and stood there. This time he noticed how her body trembled, it wasn't shaking from the cold or from fear.

It was like she was in constant pain.

"Killing demons is my job." Giyu informed the two of them, "So of course, I'll take your little sister's head off, too."

"Wait! Nezuko hasn't killed anyone!" the boy shouted in a panic, "There was a scent at my house…from someone I've never smelled before! That must be who killed everyone!"

The girl beside him nodded, the boy went on, "Not Nezuko! I don't know what's making her act like this, but…."

"That's easy, demon blood got in her wound, so she's transformed into a demon." he told them, "That is how man eating demons multiply."

The girl's eyes widened at the information, but then she sighed. "So…they're like vampires or zombies."

He wasn't sure what fantasy this girl was living in, but he saw dread all over her. He then spotted a hunting knife in the waistband of her trousers. He wondered why she hadn't used it on him or when the boy's sister literally attacked him.

But again, it wouldn't work.

"Nezuko would never rate anyone!" the boy shouted.

"A moment ago she almost ate you. The only reason she didn't, is because that girl beside you held her back."

"No! I'm sure she knows who I am!" the boy shouted out, "I won't let her hurt anyone! I'll find a way to cure her! I'll make her human again!"

The girl stepped forward and had a look of determination in her eyes, stubbornness that was a little too similar for his own good.

"I'll help him." the girl said, "She was crying, so that must mean something."

Giyu couldn't believe this girl, she was clearly ill, judging how pale her face was and her shaking body. But yet she would help this boy to cure his sister?

"She won't get better. A human who becomes a demon cannot go back." he told them.

"I'll find a way! I swear! Please don't kill her!" The boy shouted out. "I'll also find the one that killed my family! I'll do all that, so…so."

Giyu pointed the tip of his sword to the demon that he held, ready to end it.

The girl got out her knife, it had a black handle that she held firmly, she ... .was she actually planning to fight a demon slayer with one knife?

Did the girl really have that much of a death sentence? Didn't she care for her own life?

"STOP!" the boy shouted. "I can't lose Nezuko too! Please…please, stop…please…don't kill my little sister! Please…"

If anything Giyu didn't like in this life was people begging their enemy from doing whatever they're doing. How was the boy going to take vengeance just from begging?

The girl was beginning to sway a little bit, like she was about to pass out. It was only her stubbornness and survival instincts that kept her upright and conscious. He can also see her tears that were threatening to fall down her face and that made him snap.

"NEVER LEAVE YOURSELF SO DEFENSELESS IN FRONT OF AN ENEMY!" he shouted.

Giyu didn't miss how the girl flinched violently from his raised voice and the revelation was more clear about this girl than before.

She had been mistreated and abused. But by who? Her mother-father? A boyfriend, a relative or by anyone that should've kept her safe?

It also explained why she was small, too. But that didn't make him stop.

"Stop bowing so pitiful! If that worked, your family would still be alive!" he shouted at the boy, then he pointed his sword at the girl beside him. "And you, you need to take care of yourself before a lesser demon that will be able to tackle you down and tear you apart! Do you think your other father would be able to take it if he finds out about your existence only to lose you?! It would destroy him!"

The girl's eyes widened at this then she began to look sad, looking away slightly as a single tear went down and muttered something under her breath that sounded something like, "if he doesn't find me as a burden sinful."

Giyu couldn't believe she would dare to think that, but if she has been beaten down as a child mentally just as well as physically, it would be no wonder why she believes it and it sent him into the rest of his rant.

"How can a weakling like you, who bows down when it's time to fight, to kill or be killed…how can such a man cure his little sister or even find his enemy!?" he raged at both of them. "If you want something, then you must fight for it! The meek have no power and no options! The strong will crush them in every way!…demons might know how to cure your little sister, but… no demon will respect your whining and begging! They won't care if you're sick, either!"

The girl blushed slightly, "not sick."

"Then why are you shaking?!"

"I…" she looked away again for a moment, "I was under the torture curse for a while, the cruciatus curse. It's one of the effects."

"Why haven't you been treated of that!? You're just setting your nerves up to be damaged!" he shouted at her. "And for that matter, I don't respect you two either! That's reality! Before…why did you cover your sister? Did you think that would protect her?! Why didn't you throw your hatchet or your knife blade?! Why did you show me your back? That's how I was able to take her! I Should have skewered you both!"

Both of the kid's eyes widened as he said it. Even the girl slightly lowered her knife.

'Don't cry, don't despair. Those things will do you two no good. Your heart is crushed, I know your pain, how you must want to cry out. If I'd come half a day sooner…your family might have survived. But there is no turning back time.' he thought to himself. "Fill your heart with anger, strong pure anger that gives you no quarter. Anger that becomes the unwavering force that drives your limbs. Weakness and empty promises cannot protect your sister or find a cure for her. And they certainly cannot avenge your family, or help your friend find her father and to keep her safe from the magical world.'

With that thought he put the tip of his sword into the boy's sister's shoulder, which sent the two kids in front of them into action. They threw rocks at him, which he easily dodge and it hit the tree behind him.

Giyu looked to see them running past the trees, their hands behind them and ready to strike him down.

What fools they are.

He waited for them to get close, and he hit first the boy on the back then the girl at the side of her head.

But then he noticed that the hatchet wasn't in the boy's hand and the girl no longer had her hunting knife on her. Then he looked up and saw them flying towards him, he moved his head to the side as they went into the wood of the tree behind him.

'Just before passing behind the tree, they threw a rock and while hidden by the tree, both of them threw their weapons. They hid their hands so I wouldn't see that they were unarmed. Both of them knew that they couldn't win against me, so their plan…was to strike me down after I killed them.' he thought to himself, "These kids…"

Then the demon kicked him, and ran straight for both of the other two, 'no, I'm too late!"

But Giyu's eyes widened as the demon stood in front of the two kids, not eating them but protecting them.

'He wouldn't be the first one to say that and then get eaten anyway.' he thought to himself in disbelief. 'Starving demons will kill and eat their own parents, siblings and even strangers. Because they need the energy. I've seen it countless times. And must want to eat human flesh as soon as to mention the strength it took to transform into a demon, she must be doubly starved right now…this girl is injured, it cost her strength to heal that wound, but she's protecting him and focusing her anger on me.'

Then Giyu unsheathed his sword, and used the side of his hand to knock out the demon girl. He looked at the girl, he knelt down and sighed, shaking his head.

Giyu knew who her father was, but he couldn't tell her.

This girl…needs to figure out this herself. So he got bamboo and put it in the demon's mouth, using it like a muzzle and he waited for the boy and the other girl to wake up….

Author's note:

I know, I'm evil. But this is the end of the first chapter.

Now if anyone is from Japan, can you please let me know if there is something I'm writing wrong? I'm from the uk and only know a few words in Japanese but not a whole lot. So giving me hints and letting me know of any mistakes when it comes to the culture will be a great help in order to write this.