In the morning when the Kamado brother, the first one has (H/N) (H/L), eyes color are (E/C) wearing his jacket with red, black sleeves and the crescent moon behind his back, wearing the charcoal bag behind him. And the older one holding his violin case.

(Y/N): You're ready to go, Tanjiro?

Tanjiro: Hai! Nii san! I'm ready!

He smiles nodded his head looking at his adoptive brother.

(Y/N): Yeah. Let's go.

He replies with a small smiles before they head out to the village but however they're got called from their mother, their only guardian after their father pass away.

Kie: (Y/N), Tanjiro

(Y/N)/Tanjiro: Mum!

Kie: You're face is covered all by the soot, come here.

Their mother started to cleaning their face wiping out the soot with her napkins before Tanjiro takes the turn.

Kie: You boys know it's too dangerous for you with all of the snow. You two don't have to go home you know.

(Y/N): Don't worry, mum. It'll be fine, I wanted you guys to fill in with a new years.

Tanjiro: Nii san is right! We're gonna sell much of the charcoal as we're can!

Making their mother smiles at their statements.

Kie: Thank you.

???: Big bro!

Making their heads turning to owner of the voice, revealing it's brother's siblings.

Shigeru: You're going to town again?!

Hanoka: I wanted to go, too!

Kie: No you can't. You know you can't walk fast like your brothers.

She shook her for disapproval.

Shigeru: Mum!

Kie: You may not. Since he can't use the cart today, he won't give you ride when you're kids gets tired.

Shigeru: Big bro!

He sudden hugged his two older brothers.

Hanoka: I wanna go with you! I promise I help you!

(Y/N): Thank you, Hanoka. I appreciate that.

He petted her head before making her smiles in excitement and joy.

(Y/N): But, mum is right and you needed to stay at home.

Hanoka: Ehhhhhhhh?!

Making her frown in sadness.

Tanjiro: Nii san is right, but you needed to stay at home but we'll promise we might bring some goodies for you guys.

Shigeru: Really?!

Making Tanjiro nodded his head and (Y/N) kind smiles at his adoptive sister rubbing  her hair.

(Y/N): And Hanoka, I might read for you in bedtimes story when I come back and continue it And listen to my violin.

Making her smiles in joy and excitement again.

Hanoka: Really?!

(Y/N): Yeah.

Hanoka: Pinky promise!

(Y/N): Chuckles Yeah, prinky promise.

He pinky promise with his pinky finger to shake his adoptive sister's pinky finger to promise to come back.

(Y/N): That's a good girl.

Kie: Thank you, (Y/N) and Tanjiro that's why everyone love and dear for you.

Tanjiro: Yeah, we'll be heading out, mum.

(Y/N): We'll see you at home when we're returned back from work.

They both gets up on their feet.

(Y/N): And Takeo, you might be able to chops woods as many as you can?

Takeo: Sure, I can but... I hoping that we're can do it likes in old time in together.

He turns to avoid eye contract his brother.

Tanjiro/(Y/N): There, there.

They petted his brother's head until he snapped at his two older brothers.

Takeo: What's with the sudden?!

Shigeru: You're blushing big brother!

He makes fun at his older brother with his index finger.

Takeo: Will you shut up!

(Y/N): There, there. Calm down.

Shigeru: I said "Cut it out!"

Making them laughing.

Timeskip, as his mother and sibling are waving at them.

Shigeru: Hurry, back home will you?

Hanoka: Be safe, out there?

Tanjiro responds smiles back.

(Y/N): Yeah! We'll be home soon!

???: Big brother!

(Y/N)/Tanjiro: Hey, Nezuko.

Nezuko: I was putting on Rokuta down for a nap, or he'd make the scene when you two leave. He misses dad a lot when he passed away.

They rub his youngest brother sleeping on his head.

Nezuko: And everyone follows you wherever yo go.

Making them smiles at his sister's responds.

Nezuko: And big brother (Y/N)....

(Y/N): Hmm?

Making his heads turns his little sister with a small blush on her cheeks.

Nezuko: I-It is okay, that I ca-can sleep with you?

(Y/N) thinks for the minutes.

(Y/N): Sure, no problem!

Making her smiles in joy.

Nezuko: See you later!

When they're walking towards the villages until (Y/N) senses something heard from behind he quickly glances at the forest.

Tanjiro: What wrong, nii san?

(Y/N): Tanjiro, I just sense something and I detecting some of the aura on my visions can smell everything if something there?

Tanjiro sniffing on his nose he slowly glances at his brother and shook his head.

Tanjiro: No, nothing nii san.

(Y/N): That's weird, that properly a bird.

Tanjiro: Yeah.

As they're continued to walking towards the villages but they were unaware being watched by the bat behind the tree, proceed started to following and focusing on.... (Y/N).

One of the lady spotted on Tanjiro and (Y/N), all the villagers loves them seeing the brothers' kindness friendship, he always helps people.

Woman: Well now, Tanjiro and (Y/N)! I can't believe you came down here to the mountain from each day like this. You're two such a hard worker. You might catch the cold you know?

(Y/N):  Chuckles This is noting really. Do you have enough charcoal?

Man: Hey, (Y/N)?!

Making his head turns to the person.

Man: May I have some of the charcoal? Thanks for fixing my sliding doors for the other day.

(Y/N): No problem!

He gave him a thumb up.

Man 2#: I need another charcoal too!

Making them smiles but suddenly there someone with nosebleeding being lecture from the old woman escaping toward before noticing on the Kamado brother.

Man 3#: Tanjiro, (Y/N)! Perfect timing! I've been accused for breaking this plate! Help me out, will you? Sniff it! And analyze it.

Tanjiro smelling and (Y/N) shut his eyes before open it look at the broken plate and realize it.

(Y/N)/Tanjiro: It's a cat.

Man 3#: See!

Old woman: Oh my, so it was the cat?

Man 3#: I told you it wasn't me!

Making him gained of the tick marked.

Man 4#: Tanjiro, can you give me a hand for this luggage?

Girls: (Y/N)!!!

Making them flinch a little turning to a lots of girls surrounded on the Kamado brothers but they're actually a fangirls of (Y/N) love to play his violin.

Girls: We're want you to play your violin! Can you please, play it!

They begging to him.

(Y/N) turns to his brother, with a smiles nodded and (Y/N) turn back to showing his appreciate smiles.

(Y/N): Sure!

Making them murmurs in excitement, some of the people love to hear him playing of his violin, the most famous and beautiful song.

(Y/N) takes out his violin from the case, before place his head on the violin before playing of the song.

https://youtu.be/nDyGKicybYE

Making them cheer of excitement and impressive of the young violinist playing his violin.

Later, at noon. It was the time for the brothers for go home but it's getting late for him to go home.

(Y/N): Man, it's getting late for getting home today.

Tanjiro: Well, it's the good thing that we're sell much of the charcoals today, right?

(Y/N): Yeah.

He nodded his head.

???: Hey, Tanjiro, (Y/N)!

Making them turns to the old man in the hut.

(Y/N)/Tanjiro: Old man/Grandpa Saburo!

Saburo: You're going home back to the mountain? You better not, it's dangerous at night.

Tanjiro: I've got the great sense of smell and Nii san has the great sense of the sight vision of the auras.

(Y/N): Yeah, we'll be fine going home, in our business, don't worry about it. 

Saburo: I'll put you two up for the tonight. Come on, get back here.

They both looked at each other before they looked at Saburo.

(Y/N): But...

Saburo: Don't argue! Come in! Before the demons come up.

After Tanjiro and (Y/N) to their grandfather in figure's house, and they're both eating their dinner. After they finished them before getting their tea.

(Y/N)/Tanjiro: Thank you for the meal!

Sipping his tea before asking to the old man.

(Y/N): Hey, Old Man Saburo, what are the demons are like?

Saburo: Man-eating demons have always prowled the land once it gets dark.

He explain while getting futon in ready.

Saburo: That's why you should be never strolled around at night. If you're done eating, go to bed. You can set off for home at first night.

When (Y/N) and Tanjiro looking at the ceiling while in the futon.

(Y/N): Does the demon really do exist, old man Saburo?

Saburo: Yes, they're do exist, however some of the people never seen them and doesn't believe if the demons does exist but they're only appears in night never appears in the sun or they will die.

Tanjiro: These demons wouldn't it come to your house, would they?

Saburo: Yes, they do come in.

Replies with the smoking.

Tanjiro: Then, everyone would get eaten up by the demons.

Saburo: That's why the demon hunters protect us by slaying them since way back then. Light out now, go to sleep.

Tanjiro go to sleep thinking about Saburo loses his family and bringing his siblings next time and remember the memory that his grandmother use to tell him about the story of the story and (Y/N) is dreaming about.

In (Y/N)'s dream

(Y/N) opens his eyes widened, looking around the area wandering where he was.

(Y/N): Wh-Where am I?

Suddenly something just falling down to the ground, he looks up at the sky before he caught them in his bare hands looking at the rose petals.

(Y/N): Roses?

He looked on the ground suddenly, it's started to crack creating a scar on the ground where (Y/N) standing is making him creating the scar of the symbol on the ground revealing likes the shape of the bat.

(Y/N): Bat?!

The symbol started to vanished where (Y/N) was standing creating the energy crimson bats flying around making him covered on his arm to shield on his face, he makes his way through the bats surrounded on him.

Before he looking at the glowing eyes glaring at (Y/N). Making his eyes goes open in widened in shocked.

(Y/N): Wh-What the hell is that thing?!

???: Kiva..... die!

The thing started charging to (Y/N)

(Y/N) gasped waking up sitting down on his futon, breathing in and out having a nightmare.

(Y/N): Kiva? What was that?

Later on (Y/N) and Tanjiro ready to go home back to their house. Until (Y/N) opens his widened seeing his aura zooming toward the house where people has the color of black means.... death.

(Y/N): No.... it can't be.

He rushing towards going to the house and making Tanjiro to be confuse looking at his brother running in fast.

Tanjiro: Nii san, what's wrong?

(Y/N): TANJIRO, HURRY UP! SOMETHING NOT'S RIGHT AT HOME!

Making him gasped of shocked and worried.

So two brothers are running in hurried towards to their house but however.... they were too late.

Making them open in widened in fear and shocked seeing their younger sister Nezuko are laying down on the ground with Rokuta bloods on the snow.

Making them screamed in horror, rushing towards to their younger sister, (Y/N) checked on her Nezuko shook her gentle.

(Y/N): Nezuko, what's happen?! What's happened to mom and others?!

Tanjiro: N-Nii san.... looked.

(Y/N) looked at house making him stared of horrors seeing his adoptive family got killed too, he knows them because they are his adoptive family raised him like part of the family and has no memory of them.

(Y/N): No way.... Mum, Hanoka..... Takeo..... Shigeru.

(Y/N) piggyback while Tanjiro following him behind taking to the doctor to the villages in hurried before she'll die for any minutes.

Inner (Y/N): Nezuko is the only one has the warm on her body and survive. If we can get to her to a doctor, she might able to survive!

Inner Tanjiro: But how, is this happen? Was it a bear? Was it a bear that wasn't able to hibernate?  I can't breathe! The air's is so icy! My lungs is hurting me! Keep moving forward! Move your legs faster!

They knew they're couldn't keep up so they're keep going.

Inner (Y/N): Keep going! We still have the long way to go before we reach to the town. Hurry! I won't let you die! I'm going to save you no matter what! I swear as your older brother will you save no matter what!

Suddenly he heard the growling coming from the back revealing it's Nezuko with the fangs from her teeth, using her hands on his shoulder making him fall down on the edge of the cliff.

Tanjiro: Nii san!

He shouted at his adoptive brother.

Luckily he was saved by the snow on the ground.

(Y/N): That's relief then, I was saved by those snow. I slipped because of the snow to begin with. Wait what Tanjiro do.....

He looking at the top seeing his adoptive is charging jumps off the cliff and realizes that.

Inner (Y/N): Wait! Don't tell me that....

(Y/N): Tanjiro don't...

Too late, Tanjiro landed on (Y/N) making him to spit from his mouth.

Tanjiro: Gah! I'm sorry, Nii san!

(Y/N): I-It's al-allrig-ht Tanjiro...

He gasping feeling the pain when he landed on his stomach.

(Y/N): Just, don't that again, will you?

Tanjiro nodded his head.

They both get back on their feets.

(Y/N): Alright, let's go check on Nezuko.

Tanjiro: Right.

(Y/N) and Tanjiro spotted on Nezuko.

Tanjiro: Nezuko you alright?! You don't have to walk anymore!

(Y/N): I'll carry you back to town, okay?!

However she not Nezuko anymore she has become....

a demon.

 Nezuko started to growling and charging at her brothers attempting to bite him but he hold her back and uses the hatchet when she bite the wooden handle.

(Y/N) uses his aura vision seeing her auras changes the color it was green meaning human and red means demon.

Inner (Y/N): No way.... it's can't be....

Inner Tanjiro: Sh-e... she's become

Inner (Y/N)/Tanjiro: Demon!

Inner (Y/N): Old man Saburo told us about the demon. And Nezuko turn into the man-eating demon!

Inner Tanjiro: No, it's wrong Nezuko's a human ever since she was born! However, she no longer have Nezuko's scent. 

Inner (Y/N): But it wasn't Nezuko's doing! She was just trying to protect Rokuta when she was laying down, and there was no blood on her mouth or hands.

Suddenly she growing her size and her strength are stronger now. 

Tanjiro: S-She grows her size.

(Y/N): Yeah, sorry, Tanjiro.

Tanjiro: Eh?

He shoves his adoptive brother rolling on the ground away from Nezuko, he looked at his brother in worriedly.

Inner (Y/N): We're were carelessly when we're at Old man Saburo's house but everyone was brutally murdered. And I had to get Nezuko backed!

He spread his tear out.

(Y/N) : Nezuko, hang in there! Don't give in! You gotta hang on there! Don't turn into demon! You gotta stay strong! Remember me when we're play each other when we were children, and afraid to sleep in dark and you asked me to sleep with you. I won't killed you because you're my precious sister! Hang in there! Hang in there!

Suddenly there is a tear dropping on (Y/N)'s cheek making him and Tanjiro surprised  at Nezuko crying.

(Y/N): Y-You're crying..

Tanjiro looked up in the sky attempting to killed on Nezuko.

(Y/N): Looks out!

He tackles his siblings to dodge rolling on the ground from incoming slash making the blade cuts on Tanjiro's ponytail hair.

They landed on the tree before looking at their attacker.

Inner (Y/N): Who the hell is that guy?

Giyu: Why are you protecting that thing?

Tanjiro: She's our younger sister!

Giyu narrows his eyes at him and Nezuko struggles to escaped while (Y/N) and Tanjiro hold her off.

Tanjiro: Nezuko!

(Y/N): Behaved, Nezuko!

Giyu charging toward at the sibling Tanjiro tried to defend her but suddenly he notices Nezuko is gone and he looked at Giyu trapping her.

Tanjiro: Nezuko!

(Y/N): You bastard!

He started to be angry at him.

Giyu: Don't move! My job is to slay a demon like her. Needless to say, I'm going to decapitate your sister.

Tanjiro: Hold on! Nezuko hasn't killed everyone! Back at my house, that was the another scent that I'd never smell before! That's properly the one killed my family! It wasn't Nezuko! I don't know why she turned into something like that but... but still...

Giyu: It's quite simple. Because her wounds were exposed to demon's blood, she turned into a demon. That's how man-eating demons multiply. 

(Y/N): That's bullshit! Nezuko would never do that and eat of the humans!

Giyu: You're two just kidding. You're were about going to be devour from her.

Tanjiro: You're wrong! Nii san is right! I'm sure she knows who we are! We'll won't let her hurt anyone else! We're going to turn Nezuko back into human again!

Giyu: She can't be heal. Once you're turn into a demon you can never go back into a being human again.

(Y/N): You can't do that. We'll find a way no matter what! So, please... So please don't killed my precious sister!

Tanjiro: I'll hunt down the one who killed my mother! I'll make everything right! Please! Please! I begging not to! Please! Don't kill my sister! Please don't do it!

They're begging to him.

Tanjiro beg down on the floor doing the groveling.

(Y/N): Tanjiro don't do tha...

Tanjiro: I begging, please don't do it.

But it kinda made of Giyu snapped in lecture and scolding of Tanjiro's words and begging.

Giyu: Don't ever give some of the others a chance to murder you!

Making Tanjiro gasped.

Giyu: Stop doing that pathetic groveling! If it was the least bit of effective your mother wouldn't be dead! Can a weakling who can't take the initiative in such of the situation heal his sister?! Hunt down the enemy! Don't make me laugh! The weak have no right or choices! Their only fate is to be relentlessly crushed to by strong! The demons might know how to cure your sister! And don't think that a demon would respect your will or wishes! Naturally I have no respect on you, either! That's reality! Why did you throw yourself over your sister earlier? Was that your way to protecting her? Why you didn't swing your hatchet? Why did you show your back to me? All those blunders led to your sister's capture! I could've skewered her alongside with you!

He pointing his sword at Tanjiro at his harsh words and voice at the young man younger than him.

Inner Tanjiro: Don't cry. Don't despair. Now it's not a time for that. I know you're devastated. Your family was killed and your sister's become a demon. I know it's painful. I you wanted to scream! I get it. If only I'd gotten here for the half of the day sooner, everyone might not dead. But there's no way to turn back in time. Feel the rage. The powerful pure rage of not able to forgive will become your unswerving drive to take action!

Seeing Giyu preparing his sword to stab on Nezuko while Tanjiro and (Y/N) staring in helpless.

Inner Tanjiro: With such a fragile resolve like yours, you can't protect or heal your sister or get revenge for your mother!

Tanjiro: No!

(Y/N): Don't do it!

Giyu didn't listened when he stab his sword to Nezuko on the shoulder causing her screamed in pain.

Tanjiro: Stop!

He grabbed the nearby rock before threw it at him, but he deflected his sword.

(Y/N): Tanjiro!

He throw the hatchet at his brother before he caught it in his hand charging toward to Giyu, throw another rock at him but he dodge it again and Tanjiro let out of the battle cry preparing to attack on Giyu.

Inner Giyu: A straightforward attack is to driven by solely in emotion....

Giyu: You fool!

He knocked down on Tanjiro's back using his katana's hilt to hitting him on the back forcing him to fall down on the ground, causing him and her to be gasped staring at her brother on the ground. 

(Y/N): Tanjiro!

He started to charge at Giyu kept his emotionless eyes expression, he swiftly uses his foot to tripped down on (Y/N)'s leg causing him to fall down on the snowy before he could get up but Giyu stepped on him.

Giyu: Idiot! Focus and always ready on your opponent. And where his hatchet.

Seeing Tanjiro doesn't have his hatchet.

Suddenly he hear the throwing sound before looking up revealing it's the hatchet flying toward on Giyu, he quickly dodge the hatchet neck to him landed on the tree.

Inner Giyu: Just before he hid behind the tree, he hurled the rock toward me and, at the same of the time, tossed the hatchet in the air. He hid his hand when he pretended to attack. SO I wouldn't realize he was unharmed.  He knew he couldn't beat me.  He tried to bring me down after I struck on him. This kid...

(Y/N): You bastard....

He heard the growling sounds of anger making his head looked down at (Y/N) his hair covering his eyes in shadow.

(Y/N): I won't forgive..... for hurting my family!

He shouted in anger suddenly, there's an mark appeared on (Y/N)'s face liked the stained glass mirror.

Making Giyu gasped and shocked looking at (Y/N) undetected on him when his hand on Giyu's foot immune throwing him off and let go of him and Nezuko making his eyes goes open widened.

And Giyu manage to landed on the ground with his two foot in few meters away from the Kamado sibling, staring at (Y/N) glaring at him and feeling the terrifying surrounded on (Y/N)'s aura.

Inner Giyu: Wh-What is this feeling?! Is he demon?! No, this is something. What is he.

He never felt it before on (Y/N)'s auras.

He noticed Nezuko is behind him seeing her going towards to her unconscious brother.

Inner Giyu: Damn! She'll devour him!

He thought Nezuko would eat her brother but he's wrong, seeing Nezuko wasn't going to eat her brother she actually turning to Giyu to defending her brother when he's hurt her older brother. Glaring at him.

Made Giyu open widened in shocked seeing her defending him remember of Tanjiro's words.

And Nezuko charging towards at Giyu tried to slash him with her claw but he kept dodging from the attack and remembering the tales of the demon story when they don't have memory of their human live and eating human as food and seeing the girl is different from the other demons and seeing the sibling might be.

And karate chop her neck to knock her out cold.

(Y/N): Nezuko! 

He turns back to Giyu with anger looks.

(Y/N): You bastard!

He charging towards Giyu staring at him, he dodged on the side but (Y/N) gives the spin kick aiming directly to him making Giyu reacted in quickly using his arm to blocked the incoming attack causing to send flying away from (Y/N).

Giyu landed on the ground forcing him back for the bit staring at him suddenly there is a red liquid dripping on the ground, revealing it's Giyu's blood and he's nosebleeding while dripping on the ground.

Making him surprised mixture of shocked.

He covered his nose bleeding while staring at (Y/N)'s death glare at Giyu.

Inner Giyu: How.... How is this guy posses that power more then human. That humans doesn't posses that power like but however this guy is dangerous, I need to take him before he makes a move.

While (Y/N) standing with moving a muscle before he makes a move but he vanished in sight making Giyu's eyes open widened.

Inner Giyu: Shit! He vanished!

He quickly glance at behind seeing (Y/N) preparing going to punch at him and Giyu don't have time to take down or prepare taking his sword out.

Suddenly (Y/N) felt like sting at his back behind and he fall down on the ground in unconscious making Giyu confusion and surprised.

Inner Giyu: Wh-What the hell is going on? How is he unconscious when I didn't make a move unless he....

After the few minutes (Y/N) woken up looking at his precious sister Nezuko next to him wearing a bamboo around her mouth, making his eyes spread out of tears and crawling towards her before hugging her and checking on her.

(Y/N): Nezuko! Oh thanks god you okay!

He spotted his brother Tanjiro laying down in unconscious. Before he opens his eyes looking at his sister hugging her brother.

Tanjiro: Nii san! Nezuko!

He rushed towards to his sibling.

(Y/N): Tanjiro!

Tanjiro joins in the hug to console them.

Giyu: You awake huh?

Making their heads turned to Giyu standing next to the tree.

(Y/N): You!

Giyu: Go see an old man named Sakonji Urokodaki who lives at the foot of Mt Sagiri. Tell him that Giyu Tomioka, sent you. She seems to be all right since it's cloudy now, never let her to be exposed to the sunlight, okay?

Giyu vanished leaving the siblings alone.

Two brothers helping to bury their family's bodies as the grave outside of their house, they prayed that their family may they find rest in peace.

Until they heard the sound of the noise, making their head snaps in pray before turning to someone they're know villages.

(Y/N)/Tanjiro: Raigo!

Raigo: Oh my god, what happened!

Tanjiro: Raigo, you don't believe what happened....

As Tanjiro tried to explaining what happening, (Y/N) felt wince from his eyes vision activating on his aura, seeing his auras vision Raigo is not a human being, it's the colored of blue not's human.

(Y/N): Tanjiro, stay away from him! He's not human!

Tanjiro: What?!

He turned to his brother with a shocked expression.

Raigo with a knife attempting to strike on unnoticing Tanjiro.

???: I won't let you!

Suddenly something attacking him with the wing revealing.... a bat?!

Tanjiro: What?!

(Y/N): Bat?

While the bat kept attacking him with the wing while Raigo tried to swing his arms to hit the bat but bad luck, when he's fell down on the edge of the mountain fall down.

The bat release the big deep breath.

Bat: Now that guy gets out of the way.

The bat turning facing the sibling making them a comical surprised and freak outexpression seeing the bat can talked.

Tanjiro: N-Nii san.... di-di-did that bat just talked?!

(Y/N): Y-Y-Yeah.... let's just pretend that never happened.

They whispered and agreeing that.

The bat started to grinning.

Bat: I supposed we're never meet before. I'm Kivat the 3rd you can call me Kivat!

(Y/N): Y-Yeah! My name is....

Kivat: You're (Y/N), Tanjiro and your sister is the demon name Nezuko.

Making them surprised that he knows their names.

(Y/N): Y-You're not here to killed our sister because she's the demon.

Kivat: Me, no! I would never killed your sister in front of her. Don't worry, I'm not going to killed your sister and becoming one of your ally and knowing you brothers will bring back your sister as human again.

Making them heartwarming smiles that Kivat saying that kind thing to their younger sister Nezuko.

Kivat: Anyway, hurried before that thing back.

Everyone: What?!

(Y/N): Wait! Why you the thing? And how you know our name?

Kivat: I don't have time explain we need to go....

Suddenly they're hear of the roaring making them turning looking at the person.

Kivat: Oh no.

Raigo has climbed up and survived from falling down of the mountain.

Tanjiro: He's....

He started to release the big roar making them cover their ears suddenly his body transformed into likes the monster figure of horse.

Making them shocked seeing the appearance.

Horse Fangire: I smell... demon!

Making them open widened in fear, seeing him mockery laughing.

Horse Fangire: Yes, if the demon is here, that's mean I could eat her and the demon is always delicious for tasty!

Seeing his human form inside of the stained glass's surface reflections with the sinister grinning making the brothers horror in shocked meaning the monster could killed their sister in front of them.

(Y/N): I won't let you!

He charging tackling holding his stomach to hold him off to preventing getting to Nezuko. Making his brother shouted in worried.

Tenjiro: Nii san!

(Y/N): Tenjiro, takes Nezuko and run to never looked back I'll hold him off.

Tenjiro: But....

(Y/N): Hurried! I don't know how long to take.

Tenjiro don't have any word to says against his brother's word.

But Horse Fangire manage to free before he grabbed on (Y/N)'s shirt behind, before looking at him.

Horse Fangire: Fooliness....

He powerful throw (Y/N) to their house causing him to be crashed to damage the house.

Tenjiro: Nii san!!!

He shouted in worried making Nezuko spread out her tears in worried tried to reach for him but sh was holding by Tanjiro prevented her to leaving from his gripped.

The rubble landed on (Y/N).

(Y/N): Weakly Tanjiro.... run..... hurried.

Tanjiro spread his tears out had no choice to do, taking Nezuko hurried to run away from the monster.

Kivat: (Y/N)! You okay?!

He flying towards to (Y/N) stuck on the rubble.

(Y/N): Kivat! Is there anyway to defeat him?

Kivat: Yes, there is one way....

(Y/N): Really?

Kivat: Yes..... but you wanted the power?

He said in seriously making him silently in remained for a few silence before he spokes the words out from his mouth.

(Y/N): Why I wanted power? I don't care if I had no power or not, I wanted the power to protect my family and love one I care and I don't care if I live or die but however.... I wanted my brother and sister lives in happily in the future. That's why I wanted the power to protect my precious sister and brother for their safety.

Making Kivat staring at (Y/N) filled with shocked before making him laughing with mixture of impressive and joy.

Kivat: I likes the eyes of your looks and you are worthy to be my worthy.

Making him surprised and relief.

(Y/N): Really?

Kivat: Yes! But we going need to contract.

(Y/N): Contract?

Kivat: Yes! It's going a bit hurt.

(Y/N) thinks for the minutes and decided for his decision.

(Y/N): Alright, I'll do it.

Kivat: Yosha Kivatte Izukue!

At Tanjiro and Nezuko are running away from the Horse Fangire still chasing them in the middle of the snowy forest.

Tanjiro: Hurry Nezuko!

While they're running away from the Horse monster knowing their lungs will hurt and tired to run but they need to keep running away from it.

Until Nezuko tripped down by the nearby stick causing her to be fall down on the ground.

Tanjiro: Nezuko!

He rushes to her hugging her to demon ways.

Horse Fangire: Well, well, well look likes I'll my two meal.

He showing his human form on the glass stained on his body with a sinister.

Showing the invisible likes the shape of the fangs revealing it's visible to the outside making Tanjiro gasped at the scene.

Horse Fangire: Well, it's dinner time!

Before the fang strikes them suddenly the Horse Fangire got attacked by Kivat again with his wing.

Tenjiro: Kivat!

He smiles in relief.

Horse Fangire: Get off me, you stupid bat!

He tried to smack him but Kivat kept dodging him making him have a teasing smiles look.

Kivat: What wrong? Bat got your tongue?

Horse Fangire: Why you little!

And Kivat flew around before being caught the hand revealing (Y/N) got out of the rubble walking calmly towards to his sibling.

Making them smiles in joy.

Tenjiro: Nii san!

(Y/N): Sorry, I'm late but.....

He bends down to their level before rubbing his siblings' hair with a relief and kind smiles.

(Y/N): You did good job.

Tenjiro: Nii san.

He can't help the crying.

Horse Fangire: You bastard, how you get out?!

He pointing index finger towards to (Y/N) making him get up before showing his serious expression.

(Y/N): I got it from help but.... I'll show you my power to protect my siblings.

Tenjiro: Nii san.

(Y/N): Kivat izuke!

Kivat: Yosha! GABUU!

He letting Kivat biting on (Y/N)'s hand making him wince for a bit and Tenjiro and Nezuko flinch a little, suddenly the chain warps on his waist transforming into belt before his mark appears on his face again.

He narrows his eyes.

(Y/N): Henshin!

He insert Kivat on perch on upside down.

Making them shocked and surprised seeing (Y/N) transformed into Kamen Rider Kiva and the Horse Fangire trembling in fear recognizes the armour.

Horse Fangire: K-K-K-Kiva!

Tenjiro: Kiva?

Gain his head attentions about the name of Kiva.

Kiva charging towards on the horse Fangire, the fangire growling at the rider, he threw his arm to punch and he dodge under throwing the left hook punch on the chest making it stumbled back for the little.

Making the Fangire growled in anger before taking out his sword, he swing his sword at him but he blocked with his  right forearm.

Throwing the left hook on the rib forcing him back for the bit, charging slashes at him but he dodged, he counter punch on the chest and head.

He punches and kick before he powerful kick at the chest making him flew at a few feet away.

Kiva take out his red fuestle.

Kivat: Wake UP!

The sky turns crimson and the moon turns into crescent moon in the sky making his sibling surprised at the background.. Kiva kicked his right leg up as for Kivat fly around to release a chains on it. To reveal a bat red wing with three emeralds gems embedded in his shin.

Kiva than launch himself by his left leg, did turn in the air aiming to Horse fangire. Shoot him in the high speed, painful kick in the chest, and pinned straight on the ground, leaving scar of the symbol of Kiva.

Causing the Fangire glowing before shattering into pieces like the glass.

He release a deep breathe while thinking for the bit.

Tenjiro: Nii san!

Making his head turns to his brother. Seeing his brother smiles of admire of amazed in awe of his brother's fight.

Kiva: Tenjiro!

He rushed towards to him.

Tenjiro: Nii san, that was amazing!

Kiva: Y-You're not afraid of me?

He was bit surprised.

Tenjiro: Afraid? No! You're pretty amazing fighters!

His eyes filled with sparkles making his older brother chuckles for the bit under his helmet.

Kiva: You're little weirdo.

He rubbing on his hair making them both sharing a heart warming laughing.

Kiva looked at Nezuko staring at him.

Kiva: Hey, Nezuk....

He was cut on Nezuko hugging in relieve that her brother is alright. Making him to hug back with a smile under his helmet.

After Kivat got out of the belt and Kiva back as (Y/N) and the sibling looked surprised at him.

Tenjiro: Nii san! Your hair!

(Y/N): What?!

He looking at the water reflection his hair color now has the red stick with (H/C) making him surprised.

(Y/N): What the....

Suddenly he felt glowing on his back, he looked behind his back, revealing the Symbol of Kiva on his jacket.

Making them surprised.

(Y/N): What's going on?

Kivat: Well, you're awakening your Fangire blood.

Making them mixture of shocked and surprised about (Y/N).

(Y/N): Fangire blood?

Kivat: Yes, I don't have time to explain for this, but right now we're need to go.

(Y/N) looked at Tenjiro before he nodded his head while the sibling are walking to their journey finding the former mentor of Giyu...

And their story begin.

That's all guys!
This is the first chapter of Kamen rider Kiva x Demon Slayer, (Y/N) is older than Tenjiro he is 16 years old before 18 years old in 2 years ago. He will join pillar after end of the mountain arc. And he will uses and create the Breath style the power of Kiva by using his Fangire bloods.

And (Y/N)'s senses are Aura vision, it's allows him to see and detect if they are human are not in disguise and see every auras.
Green - Human, Yellow - Injury, Blue- Fangire, Red - Demon, Gold - Royal Fangire family, Silver - Not human/monster, Black - Death

Next time meeting the mentor/trainer Sakonji Urokodaki

See you later!