As two brothers, journeying travelling one of the demon slayer's former mentor. Urododaki, the former pillar of Water in Demon Slayer Corps.

And now they're currently at the villages, while (Y/N) asking them for the favor.

(Y/N): Excuse me, sir? Would it'll be alright that me and my brother if we're took that basket straw and some of the bamboo?

Man: Sure, you're welcome to get it, young man. But that basket's full of holes.

(Y/N): Thank you very much, me and brother will pay for you that.

Man: No, that's it all right. I mean it's a basket with holes on it.

(Y/N): But, it's alright. We're can pay for you that.

Man: No, it's all right. You can have the bamboo and straw for free, too.

(Y/N): But, we're going to pay you!

He and Tanjiro empty out from their pocket for the money.

Man: I said, it's okay! You're one crazy kid!

(Y/N) quickly hold the man's hand but.... he crashed his hand for the bit using his half monster's power and slammed the money on the man's palm with the mixture of their money. Making him comically shocked and disbelief in pain.

(Y/N)/Tanjiro: Please, accept this kind sir, although it's all we're got! Thank you very much!

(Y/N) grabbed the bamboo and Tanjiro has the straw and the basket while the man screamed in pain by (Y/N)'s power.

Two brother arrived back to the small cave.

(Y/N): Hey, Nezuko.

She didn't respond to her brother.

Tanjiro: Huh, Nezuko?

(Y/N) turned to Kivat sleeping on top of the tree. He snoring out.

Kivat: Hey, Kivat?

Making Kivat woken up from his sleep.

(Y/N): Where, Nezuko?

Kivat: Ah! Nezuko dug the hole.

(Y/N)/Tanjiro: Huh?

Making the brothers to be surprised, before looking at the cave inside, before Nezuko pop her head out of the hole. With a frown expression.

(Gurenge by Lisa)

(Tsuyoku nareru riyuu wo shitta) Seeing (Y/N) in the middle of the forest surrounded in the snow and the storm walking toward it, before changes in the main hallway replace by Kiva.

(Boku wo tsurete susume) Zooming in (Y/N), wearing his demon slayer uniform and his jacket, wielding his katana. Before he open his eyes. Narrows his eyes changes by the scene. Seeing Kiva flying in the straight kick with bat red wing in upside down at night with chain.

(Dorodarake no soumatou ni you) Tanjiro was landed in feet away when he was training landed next to the boulder. He gritted his teeth holding his katana.

(Kowabaru kokoro furueru te wa) His mentor Sakonji glancing at his student scenes changes Tanjiro and (Y/N) shares the small smiles for having a back before being serious in the exam facing the demon.

(Tsukamitai mono ga aru) They releases the big roar in battle cry to charged.

(Sore dake sa) Showing Sabito and Makamo are watching the brother battle.

(Yoru no nioi ni (I spend all day and night)) Zenitsu cowardly screaming away from Inosuke.

(Sora nirandemo (Staring into the sky)) While (Y/N), Tanjiro, Nezuko, are watching Zenitsu being chased by Inosuke. But Inosuke already caught him raise him in their air, struggle to get out Kamado sibling are watching in blankly and (Y/N) sigh in annoyed.

(Kawatte ikeru no wa jibun jishin dake) Showing Kanao smiling at the butterfly, changes to Genya narrows his eyes.

(Sore dake sa) Tamayo with her assistant Yushiro, and Monster trio like Jiro, Riki and Ramon playing poker inside the main hall.

(Tsuyoku nareru riyuu wo shitta) Nezuko was human once before her hair unfolded fall down, glancing at the camera wearing the bamboo.

(Boku wo tsurete susume) Showing the symbol of Kiva and changes into Demon realm and Muzan half glanced at the camera narrows his eyes. Nezuko with her brothers.

(Dou shitatte!) Kivat bit (Y/N)'s hand before his fangire marked appear.

(Kesenai yume mo tomarenai ima mo) Transformed into Kiva alongside with his brother using the breath of water, the demon are attacking shooting out arrow out from his eye hand and other demon throwing her ball smiling like maniac.

(Dareka no tame ni tsuyoku nareru nara) But the arrow red and black energy bat by Kiva using his katana and giving his brother a chance to cut the ball in half using the breath of water. Now Kiva is facing on drum demon.

(Nando demo tachiagare) Kagura is in Japanese style at outside before changes to Giyu with Pillars shown on the blade of Kiva in his citizen form, narrows his eyes as the future new Pillar.

(Sekai ni uchinomesarete makeru imi wo shitta) Now Kiva, alongside with Ixa, Taniro, Inosuke and Zenitsu is cowardly screaming. Zero slashes his sword alongside with Inosuke and Dan strikes his spear with Zenitsu strikes with thunder while Nezuko watching.

(Guren no hana yo sakihokore) And Kiva jump in the air, with the red bat wing on his right leg straight kick. Before high speeding directly to his enemy alongside with Tanjiro using the Ten breath of water.

(Unmei wo terashite) And (Y/N) holding hand with Nezuko and Tanjiro looking at the moonlight. Before (Y/N) glanced at the camera before transformed into Kiva showing his enemy on his visor like Muzan and Fangire.

Inner (Y/N): She dug a hole?

With a surprised expression alongside with his brother, before turning to Kivat.

(Y/N): Kivat, when she dug a hole?

Kivat: Hmm, a while ago.

Tanjiro: "While ago"?

Kivat: Yeah, but she really does wanted avoid for the sunlight.

Making the brothers had the curious.

(Y/N): I see, she must be really wanted to avoid the light.

He looked at his younger sister.

(Y/N): Nezuko! Be right back in any minute!

(Y/N) chopping the bamboo with the hatchet, while Tanjiro folding the basket around on the basket when (Y/N) giving Tanjiro to refill more.

(Y/N): Nezuko?! Nezuko! Think you can fit inside of this?

Tanjiro: Yeah, what nii san said. We want to keep moving during the day too.

(Y/N): I'll carry to you, okay? Can you fit here? In here? Basket.

Nezuko gets out of the hole crawling toward the basket, but too big to fit inside of the basket. Making two brother nervously seeing this.

Tanjiro: Nii san, she kinda  protrudes, huh? 

(Y/N): Chuckles Yeah.

While they were thinking about same thought when Nezuko was tiny and grow up before they're realize and know what to do.

(Y/N): Nezuko? Remember how you get big like an adult earlier? Do you think you can get the opposite?

Tanjiro: To get smaller?

They patted together on the back of Nezuko.

(Y/N)/Tanjiro: Get smaller! Get smaller!

She gets up transformed into small inside of the basket on the ground making the brothers panicked little.

They all looked at Nezuko in the basket much as the brothers' joys.

(Y/N): Ohh! Good job! Good job! That's a good girl!

He happily patting on her head making her enjoying of joy and happily.

Tanjiro: Good girl and I'm impressed.

As (Y/N) carried the basket inside of Nezuko carried by the sheet walking Tanjiro and they're talking to the woman.

Woman: Mt Sagiri? If you want to go to Mt Sagiri, you'll have to cross over that mountain, but... The sun's about to set down. Are you boys really heading there all of those luggage? It's dangerous, you know.

Tanjiro: Me and my brother will be okay.

(Y/N): Yeah, don't worry about it. Thank you very much.

They all bow down together, before they departed away.

Woman: People has gone out in missing lately. Try not to lose you way!

And they're respond back to wave at her.

Later, at night as the brother kept walking towards to the mountain before they're stopped seeing the light in the temple.

Kivat: There's a temple.

Making the brothers before (Y/N) looked at them.

(Y/N): There's a light might be leaking through.

Tanjiro: Yeah, there might be some.....

He was cut hearing the sound sound, they're confusion they turn looking around trying to find the noise.

Tanjiro: Nii san, you're hear this?

(Y/N): Yeah, but what is that comi....

Nezuko: Hmm! Hmm! Hmm!

Nezuko pointing her index finger towards on (Y/N)'s violin case. Before opening the case revealing the violin's tring started to move making the noise making the brothers surprised and Kivat recognized. 

Tanjiro: The violin started to move!

(Y/N): Yeah, what is go....

Kivat: Bloody Rose....

Making them turns to Kivat flying in the air with his wings.

(Y/N): Kivat! You know the name of the violin?!

Kivat: Yes! But the Bloody Rose alerted us in something.

Tanjiro: Alerted of what?

Kivat: Danger...

Making (Y/N) activate his Aura vision seeing inside of the temple, the black aura color being eaten by the red aura of demon.

And his normal turns back into normal.

(Y/N): Oh no! Tanjiro, stay here with Nezuko and Kivat with me!

Kivat: Got it!

(Y/N) left Tanjiro holding his violin case hurried rushing towards where the temple is with Kivat and Tanjiro looked in worried and decided to follow him.

(Y/N) open the slide door, making his eyes in horror, seeing the dead body of the man being eaten by the.... two demons.

Demon 1#: What the hell?

Demon 2#: This is our turf.

Demon 1#: If you break into our territory.

Demoon 1/2: We'll make you pay!

Two demon glare at (Y/N) with the blood on their mouth.

Making (Y/N) gritted his teeth.

Inner (Y/N): Shit! It's the man-eating demon!

His adopted sibling secretly behind him their eyes become widened up in horror seeing the demon eating the man alive.

While the demons are licking and cleaning their fingers.

Demon 2#: There's something about you.

Demon 1#: Yeah, are you three are humans?

Made (Y/N) raised his eyebrow in curiosity. 

Inner (Y/N): Three? Don't tell me...

He turns at his sibling behind making them to be gasped.

(Y/N): What are guys doing here?!

Tanjiro: Sorry, nii san! We're just wanted to fol...

(Y/N): Guys, get out of here! It's too dange....

He was about to scold them but he was cut by the two charge towards on him tackle him, making the siblings worried.

Tanjiro: Nii san!

As the demons were about to eat him but (Y/N) quickly using the hatchet and the knife in the reversal grips, slicing on their throats. (Y/N) landed on the skidding skidding for the bit gritted his teeth seeing as the demons on the ground to flipped up.

Demon 1#: Hehehehe. A hatchet and the knife, huh? Not bad.

Demon 2#: But the scratch like this, but it'll be heal in no time.

As both of the demon were able to regeneration, making his brother gasped in shocked and (Y/N) narrows his eyes in coldly as he continued to glare at them.

Demon 1#: See that? The bleeding already stopped.

They both grinning like crazy.

As (Y/N) tossed his weapons away on the ground, they confuse for the bit and then they're started to laughing.

Demon 2#: Man, you're really a idiot! What will you do, without your wea...

(Y/N): Kivat....

Making them confusion.

Kivat: Yosha Kivat Izuke!

Kivat flying around in cheerful before being caught by (Y/N) in his hand.

Kivat: Gabuu!

He bit on (Y/N)'s hand. Making his marked appear and the belt appeared on his waist.

(Y/N): Henshin!

He placed Kivat on the perch on upside down.

Making the demons to be shocked seeing his sudden appearance transforming into Kiva. Trembling in fear.

Demon 1#: W-W-What is that armour?!

Demon 2#: I don't know! Let killed him before he killed us!

Demon 1#: Y-Yeah!

Kiva: Tanjiro, take Nezuko and find some cover.

Tanjiro: Y-Yeah!

He nodded his head, taking to Nezuko where she watching the dead body of the people in horror.

Kiva stance charging to them and the demons growled back. Before they're charge at him. Kiba throws his punch on left side and the first demon punch back. Their fist collides in the middle, making a little shock-wave.

Suddenly, there's the sound of the crack sound, Kiva overpowered the demon's fist, making the bone to be broken and screamed back. Making hims stumbled back before being caught by his fellow demon.

Demon 2#: Hey, you're alright?!

Demon 1#: I'm fine. Now that....

His eyes become widened in shocked seeing his broken wont't be able to heal or regenerated.

Demon: W-W-What?! Why?! Why IT WON'T BE HEALED!!!

Until they hear the sound of hehehehe, coming Kivat talking on the belt.

Kivat: That's too bad for you. The demons like you, won't be able to heal up or regenerate by the power of Kiva's power. You thought you might be destroyed by the Demons Slayer corp, right? But too bad, you're about to get killed by Kiva.

Demon 2#: No way! 

Demon 1#: You're lying!

Kivat: Sorry, but I'm not wrong!

Making the demon click their tongue.

Demon 2#: Dammit! You'll take the brat and I'll be taking that guy!

Demon 1#: Right!

He dash in high speed towards on Tanjiro tried to get Nezuko away but he being caught by the demon choking on his neck on one arm.

Kiva: Tanjiro!

Demon 2#: Focus on your enemy!

He quickly turned seeing he was scratched by the demon with the claw, sparks came out from armour, sending him flying on the ground rolling the ground.

He get up so quickly, turning his heads towards the demon.

Kiva: Why you!

He tried to attack him but bad luck, the demon vanished, making Kiva surprised at his ability.

Kiva: He's vanished?

Suddenly the demon reappears with the sadistic grin, he slash on his back making him nearly fall down, Kiva tried to attack him quickly turns. Vanished again before reappears scratching on his back. He struggles to find and attack when the demon vanished and reappearing to attack him.

Tanjiro: Nii san!

Demon 1#: All right, you're going to get suffering seeing your brother to be dead once he get out of his armour!

Inner Kiva: He's teleport? No, it must been his ability. Using his ability on the leg making him run in fast that I can't able to see. I need to wait before he gets closed to me.

He shut his eyes under his helmet without moving it in silently.

Demon reappers behind him in close smirking before attemtpting to scratch on him with his claw.

Demon 2#: You're mine now!

Inner Kiva: Now!

He quickly turns before grabbing on the wrist in tightly making the demon to be shocked at his sudden movement.

Demon: Nani?!

Making Kiva smirked under his helmet.

Kiva: Got you now bitch!

He throws his punch on the demon's chest, making him spit out of blood. He rapidly goes fast kept punching him. Before he let's go of his arm and throws thew powerful punch send him flying towards the forest.

Making the other demon to be shocked.

Demon 1#: I-Impossible! How is that human had this po....

He was cut when Nezuko when Nezuko kick his head off separate from his body. Making Tanjiro screamed get the body of him.

Kiva: Nezuko! Tanjiro!

He rushing towards his shipping in relief.

Tanjiro: Nii san!

Kiva: You guys alright?

He rubbing on Nezuko is enjoying this and Tanjiro with worried expression.

Tanjiro: N-Nii san, it's not over yet! The demon is...

Kiva: Watch out!

He move Tanjiro away, the his immune punch sending him flying towards on the tree.

Inner Tanjiro: H-He can move, without his head!

???: You bastards!

Making them turned towards on the same demon that Nezuko kicked earlier. He glaring at the sibling.

Demon 1#: And of you is a demon after all? You gave off such a weird vibe? What's a human with armour man and demon doing team up!

Inner Kiva/Tanjiro: He actually talking!

Kivat: (Y/N)! Tanjiro! Nezuko! The battle is not over yet! There gonna be another battle!

Inner Kiva: What the hell, I thought Nezuko killed him! But maybe... If I can killed him.

Suddenly he tackled by the same demon that (Y/N) punch him through the forested, he looked at his face filled with rage.

Demon 2#: YOU BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAASTARRRRRRRRRRRRRRRRRRDDDD!!!

Kiva kicked on his stomach to off him, and Kiva landed on the land, seeing the Demon gets up and vanished using his super speed.

Kiva: Dammit!

Kivat: (Y/N)! Take out the blue fuestle!

Kiva: Blue Fuestle?

He take out the blue wolf like the shape of head fuestle, showing on Kiva.

Kiva: You mean this?

Kivat: Yeah! Put on me!

He nodded his head, before placing the Garulu fuestle on the kivat.

Kivat: GARULU SABER!

Meanwhile in the meanwhile, there is a man in his middle age, hearing the sound of the whistle in the main hallway while playing the card.

Jirou: So, that kid actually awaken his power and summon me? Chuckles He does remind me of his father.

He gets up from his seat, before kneel down on the floor, scratching on the floor with his claw. Showing his true form covered by the auras.

Transformed into like the small werewolf statue.

As the orange orb were sent towards on (Y/N)'s direction.

https://youtu.be/djgvXE1E1vQ

(Skip to 0:48 end 1:09)

Making them to be shocked seeing Kiva changing into a new form.

Demon 1#: W-What?!

Tanjiro: Nii san, changes form!

As the demon gets closed to Kiva, but he blocked on his sword black on the finger nail claws, before Kiva grabbed on the hair behind of the demon and headbutted on him hard. Forcing him fall back on the ground to sit.

Kiva started to growling and howling sound like Werewolf, he stance likes the wolf on low on the ground with his blade.

Tanjiro sniffing his nose to smell on his brother.

Inner Tanjiro: T-That smells! Nii san is acting like... like.... werewolf!

Seeing on Tanjiro's vision the Garulu aura appears on Kiva.

They both charging towards in high speed, they both slashing on their weapons in high speed and the sparks came out from their weapons. And the demon using his super speed to vanished reappears again behind him

The demon using on his arm to stabbed him with his claws but Kiva quickly reacted turning his sword into reversal grips, swinging his sword to cut of his... arm on right side.

Demon 2#: Arghhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh!

He screamed in pain holding where his painless before glancing up seeing his arm started to fading away.

Demon 2#: M-My arm!

Kiva: It's worked! Kivat you're right!

Kivat: Hehehehe! Yeah, I am!

He grinning in cheekly.

Demon 2#: You bastard, you'll pay for my arm!

Kivat: Kivat!

Kivat: Yeah! Place the blade on my mouth!

He nodded his head.

He place the saber on Kivat's mouth, he bite it.

Kivat: Garulu Bite!

He heldly grips on the sword, soon the sky turns crimson and moons turns into crescent moon in the sky. His mouth plate sudden opens and bit one of the handle of the sword, before making the move of the poses for the bit.

He growled like the werewolf and the demon trembling in fear.

And Kiva towards to him, moving like the werewolf, before leap up in the sky to next to the moon, shooting him aiming towards the demon, in high speed. While he rolling around, the demon reacted quickly using his claw to defend himself. However the claws nails were cut and painful slash. Causing him to screamed in pain leaving the aura symbol face of Garulu before causing the explosion and die.

Making them shocked seeing Kiva destroyed the demon without cutting the head. The head stuck by the hatchet trembling in fear seeing this.

Demon 1#: I-Impossible! I thought we're demons cut in head and die but h-h-how is this possible!

Kiva growling like werewolf before glancing to his precious little sister the headless body attacking her.

Kiva: Don't you dare....

He turns his sword into reversal grips.

Kiva: HURT MY PRECIOUS LITTLE SISTER!!!

He immunity throwing his sword aiming towards on the headless demon. Powerful stabbed through the body where the heart is. Making the body fall down.

Causing the head demon spits out blood from his mouth, struggle to get the hatchet out from him.

As Kiva walking towards to her.

Kiva: Nezuko, you alright?

He was sudden hug by Nezuko and hugged back before rubbing on her head, seeing a little tear forms her eyes.

Kiva: There, there, there.

Tanjiro: Nii san!

Kiva: Tanjiro....

He flinched hearing the sound of anger and disappointed. Seeing him getting up on his foot.

Kiva: Tanjiro, first you disobeyed me and then didn't run away to get safety.

Tanjiro feeling down and fool, knowing that his brother was right and scolding him.

Kiva: But....

He sudden rubbing on his head making him surprised and confusion.

Kiva: You do some bravery efforts. I proud of you.

Tanjiro couldn't himself helps him with smiles and tears from his brother's praising.

Kiva: And....

He slowly turned to glare at head flinch trembling in fear and see the sweating from his head.

Kiva: You're next....

He said in coldly.

Taking his sword out from the demon's body, walking towards the demon struggles to escapes, As he moving when he put the blade down on the ground making form a spark while he's walking.

Demon 1#: Don't come near me! Stop! Stop you bastard!

Kiva preparing to stab on the demon to meet his... death.

Before he could killed him but however, he was stopped by his brother placing on his shoulder pad.

Kiva: Tanjiro?

Tanjiro: Nii san... Let, me finished this.

Making Kiva looked surprised.

Kiva: Are you sure? You're never done it before.

Tanjiro: Hai, nii san. Please, let me do it.

Making Kiva stare at him in minutes before he shook his head.

Kiva: Okay.

He cleared the path for his brother but however, he knew his brother to be weak has kindness on him, decided if he can kill him or not.

But he was stopped the man placing on Tanjiro's shoulder, making them turns to someone wearing a.... goblin masked?!

???: You can't finish him off.

Inner Kiva: W-What the! I didn't see him, here.

Inner Tanjiro: G-Goblin?

As the Tanjiro asked him to how it's finished, but the Goblin Man refused to asked and telling him that to use his head. Tanjiro used the rock struggle to move and killed the demon and Kiva and the Masked man knew that, he can't kill the demon has the kindness inside of him.

Making Kiva sigh out of tiredness.

Kiva: Sorry, Tanjiro.....

He moves his little brother out of the way and the Goblin masked man peak interesting.

Kiva: You don't want to see this....

Kiva preparing to strike his sword towards on demon, stabbing through his eye at the end of the tree. Making the demon screamed in pain making Tanjiro gasped and the masked man raised his eyebrow under his mask.

Demon: Y-Y-You bastard! Ho-How dare you to stabbed my e....

He was cut when Kiva quickly swing his sword to cut one of the arm where it's under of the head making it's screamed in pain again.

The masked man looking at the arm been cut, it's suddenly faded away making him to shocked seeing this and then glance up seeing the eye, arm hasn't been regeneration and before turning to the headless body hasn't been respond to moving.

Goblin masked man: The boy uses his powers and sword, to cut and beaten the demons however, their bodies seemed to be prevented to be able of regeneration. And this is clearly impossible that we're never seen before. It's might be the one stopped and killed the demon without killing their head. This man....

Seeing Kiva grabbed one of the hair, his face getting closer to his and the demon trembling in fear seeing his glare. The visor started glowing.

Kiva: Listen up, you bastard! I hadn't forgiven for hurting my family and eating of the innocent people you had eaten to. And... Enjoy in hell.

Demon 1#: Enjoy in hell?! Listen up you bastard I'll....

He was cut seeing the sunset rise up, making him screamed in pain and tried to shield his single but bad luck. He die started to faded away.

Kiva: That's why.

Making Tenjiro to be panicked and fear and realizes that.

Inner Tanjiro: He's gone with that much sunlight?! No wonder why Nezuko shrinks from it.

Making him realize that Nezuko isn't here before he could screamed in panicked.

Kiva: Nezuko, it's all right. I had use my aura vision to detect where she is. She inside of the temple. Go check if she all right.

He nodded his head.

Rushing to check to she all right, seeing Nezuko hiding under of the futon with a frown expression.

Kiva looking at the tree where, he stabbed and cut of the demon.

Inner Kiva: Good thing, he just shut up. But....

He looking at his own hand.

Inner Kiva: There's one thing, I wanted to know. What am I? How I able to killed one of the demons. Am I human or not.

Until Kiva turns his head towards on the same man wearing the masked started to pray at the dead body.

So, two brother walked approach him.

Kiva: Um, sir.

Urododaki: I'm Sakonji Urododaki. I'm assuming that you're two boys Giyu Tomioka sent in my way.

Tenjiro: Yes! This is my big brother, (Y/N) Kamado! I'm Tenjiro Kamado! This is our little sister is Nezuko, and...

Urododaki: Tenjiro....

Making his head turns to the brother.

Urododaki: What will you do when your sister devours of a human?

This question caught off guarded them.

The old man started to walking to Tanjiro and then slapped Tanjiro. Making them surprsied.

Kiva: Tanjiro!

Urododaki: You're failed to finish off that demon before your brother could stabbed his eyes before daybreak. Do you know why you wouldn't answer my question right away? It's because your resolve was too weak!  There are two things to do is your sister devours human. Kill your sister! And slit your own belly and die! That's what it means to travel with your sister who becomes a demon! But that must never happen no matter what. And you'd best not to forget. Your sister, taking the life of an innocent person... That's the one thing that must never happen. Ever! Do you understand what I saying?

Tanjiro: Yes!

Urododaki: And you!

He pointed index finger to Kiva making him flinch a little.

Kiva: Yes, sir!

Urododaki: I don't know how you done it, without killing of their heads and stopped their regeneration. But however I wanted to know if you human or not!

Kiva: Yes! 

He nodded his head.

Kiva: Kiva, undo my transformation.

Kivat: Very well, (Y/N).

Kivat gets out of the belt, making him reverted back into his human form.

(Y/N): Is this good, sir.

Urododaki: Yes.

Inner Urododaki: However, that boy I smell about. He has human blood but however, he's half human and the other blood I've never smell it before. What is this boy. Is he allies or our enemy of humanity?

Urododaki: All right, now I'm going to test you to see if you're fit to become a member of the Demon Slayer Corps. Carry your sister on the back and follow me!

As Urododaki running in fast on the ground, while Tanjiro and (Y/N) catching up on him and surprise seeing him run in fast. 

Inner (Y/N): He's fast! Just how old is that old man?!

Inner Tanjiro: Just like earlier, I'm not hearing any of the footsteps at all!

Inner (Y/N)/Tanjiro: Nezuko, I know it must be jarring, but please be patient! Well being patient is all that you've ever known.

Remembering the flashback in (Y/N)'s mind, Nezuko crying that she accidently hurt her knee, and so (Y/N) comes to her being piggyback and smiles of happiness resting on his back. And Tanjiro's mind seeing her kimono has been ripped suggesting they're buying another one. But Nezuko said don't worry about it. 

Inner (Y/N): Your big brothers will promise you that, we'll bring you back into human again!

Soon as the brothers arrived to the old man's house, while catching one of their air in tiredness when they're resting for the bit.

Tanjiro: N-Now, have I... passed the test?

As the old man removed the hooded scarf of his head, before sliding the door open.

Urododaki: The real test starts now. We're going to climb up to the mountain.

Making Tanjiro screamed in panicked.

And so, (Y/N) declines and suggested that he might watching for his sister, so Tanjiro and Urododaki taking him to the mountain. Leaving Tanjiro alone and realizing that the old man set up the booby trapped for him.

In order to passed the test, so Tanjiro had to use his nose to smell to detect the booby traps, to avoid them.

After he accomplished the test and Tanjiro returned back to Urododaki's house.

And Urododaki started to remembering of the letter being sents by his former Giyu. Sending the requesting taking care of the 3 sibling and asked Tanjiro to favor for him that he will be training under by him. 

Urododaki: I accept you..... as my student Tanjiro Kamado.

And so, Urododaki making the hot pot for the boys, while (Y/N) staring at Kivat waiting for the answer.

(Y/N): Okay, I wanted to know about the armour name Kiva.

Tenjiro: Yeah, what the monster about, we're never seen it before.

Urododaki: Monster?

Making Kivat sigh and knowing had no chance.

Kivat: Very well. (Y/N). You are not human. You're half human and half fangire.

Making them to be shocked at his statement.

(Y/N): W-What?! What you mean that?

Tanjiro: Wait! Nii san is half human and half monster?!

Kivat: Yes, it's the term of the Fangire are the type of vampire monster their body are like the stained glass monster, they're like to feed of human's energy life force. They're using the glass shard like Life-Sucking Fangs to drain their life energy to maintains their soul.

Urododaki: But, how can come we're never heard of that?

Kivat: Because, they're hiding from the humans society in disguise, to taking their energy life form to feed.

Tanjiro: Wait! Nii san is not like the othe.....

Kivat: I know that. But however, (Y/N) still has his human side stays remain, he is still care for you and Nezuko.

Making the two brothers smiles at kivat before they realized of...

Tanjiro: Wait! What you mean of Nii san has awakening his Fangire's powers.

Kivat: Because, he gains of emotion when he's in rage seeing his love one gets heart but he posses the super strength, super speed, super agility, super senses. That his from his fangire power.

(Y/N): I see, it must been my powers under my Fangire's blood, right?

He looking at his hand.

Kivat: Yes, however, you must master those powers.

(Y/N): And see, but what about Kiva? How those guys afraid of the armour.

Kivat: Chuckles That's a good question. Over the centuries, the first Fangire King has the kind and the beloving king by the humans and fangire. He wanted humans and fangire to co-exist in peace but his kind refuses that peace with human could die. But fangire king decided to creates the special armour known as..... Kiva. The first Kiva. Kiva acting the protector towards on humanity against the fangire. We're as Kivat acted their partners for generation to become next Kiva.

Tanjiro: Wait! Your family had been generated with your family?!

Kivat: Yes! As you can see, you my father was the previous Kivat with his partner. And so my father left me to searching for my partner. So that's how I found (Y/N)!

He spokes in proudly, making him smiles before petting on him.

(Y/N): Good thing, you're just here.

Kivat: Yeah!

He grinning.

Tanjiro: And, can human transformed into Kiva? And are they allied with demon?

(Y/N): Tanjiro!

Kivat: But sadly, no. Human cannot kiva transformed only the one with Fangire's blood is able to transformed into Kiva.

Tanjiro: I see, I didn't know that...

He frown and down.

Kivat: No, no, no it's fine! But the other question is that demon and fangire.... never gets along.

Making them surprised at Kivat's sudden question in seriousness.

Tanjiro: B-But why?

Kivat: As you can see, Fangire and demon never worked together and never gets along, because Fangire existed first seeing the demons taking their dinner known as human but if they're eats their food and they're eat them taking of their energy life force. So any question?

(Y/N): N-No, that's would be all.

Kivat: I see, then let's eat!

He returns to his cheerful expression, going to eat all of the eats.

Later, at night so when the people finished eating of their dinner. (Y/N) is packing his stuff up. Quietly going to the door.

Urododaki: So, you're really go out?

Making him flinch before turning to Tanjiro and Urododaki standing.

Before he could say any words but he sigh decided to tell them.

(Y/N): Yes.

Tanjiro: B-But, Nii san, why?

(Y/N): Answer....

Made them surprised for the bit.

(Y/N): I needed to find the answer for about my origin and the demons asking them for curing Nezuko back into human. If they're refuses say it. I'll killed them.

Seeing on his eyes filled with coldness. 

(Y/N): And Mr Urododaki, can you take care of my siblings and train my brother into the swordsman when I'm away going to finds some answer.

Urododaki: Yes, of course, you can leave it to me, young man.

He nodded his head.

(Y/N) turns to his brother with the hint of sadness of his eyes.

(Y/N): And Tanjiro.....

He was cut by Tanjiro sudden hug on him, making him surprised before he hug him back, with a small smiles. Seeing a small tears on his eyes.

Tanjiro: Make sure, you promise to come back when you're return to safety, right?

(Y/N): Yeah. I'll promise.

And (Y/N) looking at Nezuko sleeping on the futon in peacely, before he place a kiss on her forehead.

(Y/N): I'll come back to you. I promise.

As (Y/N) waving goodbye to Tanjiro and Urododaki he left walking journey with Kivat, with the determination looked to find out about his origin and then going to the interrogates the demon how to bring his sister back into human again and find out who murdered his adopted family.

Inner (Y/N): I'll come back, I promise.

He clenched his fist into ball.

But (Y/N) was unaware by someone watching.

???: So, the former queen's child has live. Chuckles Soon, you'll meets your end.... your majesty.

He vanished without a truce.

To be continued!