(btw my story may not follow the original plot of jjk at some points because you will have your own little adventures and interactions with other characters and since you are Rengoku almost everything you say will be in caps because he has such a loud, booming voice)

Act 1: Getting to know the world

As you close your eyes the last thing you saw was your mother standing behind Tanjiro congratulating you on a job well done. And with that you took one last look at her and gave one of your biggest most brightest smiles taking your final breaths. Dying happily knowing that you have completed you duty on not letting anyone die. As you took your final breath the last thing you hear is Tanjiro's cry of sadness as your world goes dark.

(time sk-KING CRIMSON)

As you open up you eyes you see that you are not in the same place when you died except now you are in some sort of old run downed building. Your eyes widen as you sense something lurking. So you get up and look around for the demon and as you run down the hallways of this old building you find yourself getting lost 

Y/N: "THIS IS GONNA TAKE A LONG TIME" your voice boomed down the hallway grabbing the attention of anything that is in the building 

As you are running down the hallway you see your first demon

Y/N: "HAHA IT SEEMS THE DEMONS HAVE FOLLOWED ME HERE. NOW TO TASTE MY FLAMES, FLAME BREATHING FIRST FORM: UNKNOWING FIRE" 

As you shot forward giving no time for the demon to react, your sword had already sliced off the head from it's neck.

Y/N:  "NOW TIME TO FIND A WAY OUT OF HERE AND KILL ANY DEMONS ON THE WAY OUT"

(Three days later...) (3rd POV)

As the quartet made their way towards "Roppongi" they are soon to be bamboozled by their Sensei and end up in front of some old building that our "cute little swordsman" is currently living(lost) in.

Fushiguro: "There is a curse here"

Yuuji & Nobara:  "YOU TRICKED US" they both yelled at our man-child Sensei

"There is a big cemetery nearby . The double the whammy of that and an abandon building that brought out a curse" Gojo said completely ignoring them 

Yuuji: " So they really do pop up more often around graves"he asked 

Meanwhile Nobara was complaining while doing this little spinning move. 

"The issue isn't the cemetery itself. It's the fact that people keep associating cemetery with fear" Fushiguro answered him 

Yuuji:"Oh it was the same for schools wasn't it"

"Hold up he didn't even know that yet" the orange haired girls asked 

"To be honest..."the black haired male said

"He swallowed a special-grade cursed object" She yelled as she walked away from them "Gross! Unbelievable! That's so unsanitary and disgusting! No way! No way! No way! No way!" she crossed her hands in the form of and X in front of her.

Yuuji:"What?" 

Fushiguro:"I agree with her"

"I want to know what all of you are capable of. Just think of this as a field test" Gojo told them then continued "Nobara, Yuuji, you two go exorcise the cures inside the building"

Nobara:"Geh"

Yuuji:"Huh? But I thought only curses can exorcise curses, right? I cant use any jujutsu yet."

"You're basically half a curse already. There's cursed energy flowing through your body. Though controlling that energy isn't something that happens overnight" the grey haired male said while giving his student a cursed weapon 

"It's the cursed tool, Slaughter Demon. it's a weapon that is imbued with cursed energy, So it'll work on curses, too"

"Lame" Nobara said putting on her belt while walking towards the entrance with Yuuji behind her before being stopped 

"Oh and one more thing. Don't let Sakuna. If you use him, you'll get rid of all the curses nearby in a flash, but you'll also drag everyone around you into it"

Yuuji gave him the thumbs up saying "Got it, don't let Sakuna out" 

"Hurry it up" Nobara called out.

"Yeah. yeah"

"Go on n-" 

"UMAI" 

They all flinch at the loud voice that had come from inside 'huh that was weird I guess there is someone else inside the building' they all had thought as Yuuji and Nobara made their way towards the building 

Inside the building

As the duo walks around looking for the curse they notice lots of piles of black ashes everywhere... 

"What a pain. Why do I have to deal with curses after coming all this way to Tokyo" She said while walking up the stairs 

"Huh?,Didn't you come here to exorcise curses?" Yuugi asked her    

"Lets save some time and split up. I'll start from the top and and go floor by floor. While you start at the bottom. Lets get this over with quick and grab sushi from Ginza"

"Hold on a minute. Lets take this a bit more seriously. Curses are really dangerous, you know"

The Girl the walked back down the stairs and kicked the fella making him spin around before falling on the ground 

"I don't want to hear it from someone who was a normie until recently! Now get moving!" She exclaimed then turned around and walked back up the stairs 

"Your emotions have been all over the place today" Yuuji said 

"This is why girls don't like you" She spat back at him 

"How did you know they don't like me?!" he said "Are you even popular enough to talk? Bitch."

With Nobara

Nobara had entered a room and stopped "Hey you, curse" She called out to the curse that looks like a mannequin.

"I mean you, mannequin in the center. You actually think you are hidden there?" she then had nails and a hammer had appeared in her hands while doing a pose   

"If you won't come out I will just exorcise you there"

Outside the building 

"But Kugisaki has experience, right? Little late for that now ,isn't it?" Fushiguro said 

"Curses are born from human minds. So their strength and numbers grow in proportion to the population" The other man answered 

Inside the building

Suddenly she then threw the nails and blue like flames had surrounded the them appeared. She then hit the nails with her hammer making the nails fly towards the mannequin, Hitting it square on the head 

The curse then leaned back and opened it's eye....and then more eyes had appeared and it stood back up 

"You might want to pull those out.." She then snapped her fingers making the nails dig deeper in it's head "Or else my cursed energy will flow into you"

Then it's head exploded , and it fell down not moving .

'Nailed it' she thought smiling to herself Then a noise was heard making the female alert 

A slab of wood had fallen ,only to show a small child who appeared to be tearing up.

'A child? Must have snuck in here for some fun and then encountered a curse' she thought as she approached the boy  

"It's okay, you can come out now" She called to the boy 

The boy shook his head saying" He told me to stay here until he got back"

"Huh?" she said in shock but then cleared her throat. She turned around saying "I guess it is true that kids don't warm up to beautiful women. Guess I'll call Itadori"

"Wait don't leave me here" the boy called out making her turn around. Suddenly a curse had appeared through the wall grabbing the head of the boy 

The curse then shook the poor boy around 

The girl was gonna throw her nails at the curse until she saw it put it's own nail up against the kids neck 

'it's taking him hostage? this curse has intelligence?' She thought as the curse had started applying pressure on the kids neck making him bleed.

"Damn it, Damn it, Damn it, Damn it!" She screamed out 

'this curse isn't even that strong!  Grade 4....maybe lower like a low grade 3, but it knows that! and that is why It took the boy hostage! calm yourself down. If the I die then the boy dies as well. But if the child dies, I won't die. Logically speaking , it's better if I survive, at least'  she thought as she threw down her hammer and nails and put her hands up in surrender 

"I'm unarmed. Let the boy go"She said to it 

The curse only grinned as the boy trembled in fear 

'I'm such an Idiot! See? it's not letting the boy go at all'  she thought then looked down " I wish I could have seen Saori-chan one last time" 

Just then a fist came though the wall "Huh? I missed?"  

Then the wall had crashed down revealing Yuuji

The creature had backed away from him putting his nail put to the boys throat.

But before anyone could make a move, the smell of fire had filled the air and at blinding speed and man in a white and red cape with a ferocious smile and a sword that had fire coming out of the hole that Yuuji had made and cut off the curses arms and the boy falling into the mans arms 

"Are you okay" the man said gently to the boy as if he was trying to calm him down 

"uh-huh" the boy replied, now calm at the sight of the man 

The creature had tried getting away from them by going through that wall 

"It's getting away" Yuuji had said 

"I don't think so! Itadori! Give me that arm!" Nobara had said while opening her outfit to reveal a doll. She then threw the doll on top of the arm  "A straw doll?" the boy asked "Creepy" Itadori replied "INDEED IT IS STRANGE" The man had boomed.

And as another nail had begin to light up in blue flames she said "Straw doll Technique: Resonance!"

This had caused the curse to become filled with metal spikes.

Time skip (Y/N) POV

As I sat down with the boy on my lap as I can see the other two people arguing to each other about it being dangerous or something and somehow they did not acknowledge me yet.

"Thank you for looking after me Mister Rengoku" the boy said all quietly

"IT IS NO PROBLEM BECAUSE IT IS MY DUTY TO PROTECT THE WEAK SO THAT THEY COULD BECOME STRONGER" I told him because I didn't want to tell him that I was acutally trying to find a way out for the both of us because I had got lost, 

The boy flinched at my loud voice to which I felt a little bad about.

"You're really warm sir" he said as he started to hug me 

"Really? I had no idea" I said while laughing.

And now that I had got a good look at them I saw that it was a boy with pinkish hair and a orange-ish haired girl that had been styled in a bob-cut

(Itadori POV)

As me and Kugisaki had begin to walk up to the boy and man. The man had used some sort of fire move and he kinda looked like Rengoku from demon slayer so I decided to compliment him

"Hey nice cosplay"I complimented the man 

"COSPLAY? I HAVE NO IDEA WHAT THAT MEANS" He replied 

 "Yeah cosplay, you know, when you dress up like a person that is real or not real"

"I HAVE BEEN WEARING THESE TYPES OF CLOTHES FOR A LONG TIME" This took me and Kugisaki aback and for some I can feel myself getting excited   

"Wait what is your name?" Nobara said getting a little excited herself

"MY NAME IS (Y/N) RENGOKU, THE FLAME HASHIRA OF THE DEMON SLAYER CORP" he said as he introduced himself 

"And how did you do that fire thingy?" I asked 

"THAT WAS MY BREATHING TECHNIQUE" he answered with that smile never leaving his face 

(3rd POV)

'OMG IT REALLY IS HIM!!!'  Both Nobara and Yuuji had thought (A/N: Remember these two share a braincell)

Yuuji: "So wait how did you get here?"

Y/N: "I AM NOT SURE BECAUSE LAST THING I REMEMBER BEFORE BEING HERE WAS ME DYING TO THE HANDS OF UPPER MOON THREE OUTSIDE THE TRAIN" 

Yuuji and Nobara: 'Did we just get the movie spoiled for us?'

Nobara: And how long were you here for? 

Y/N: THEN WHEN I CLOSED MY EYES I HAD DIED, BUT WHEN I HAD OPENED THEM I HAD FOUND MYSELF LYING DOWN LOOKING AT THE CEILING, SO I SPENT THREE DAYS TRYING TO FIND A WAY OUT BECAUSE I WAS LOST"

Yuuji & Nobara: THREE DAYS?!?!

Boy: Mister Rengoku, I thought you said it was because you wanted to kill everything in the building"

(Y/N) then gives out a small embarrassed chuckle 

Y/N: YES THAT IS WHAT I WAS DOING AS WELL 

Nobara: 'I cannot believe that my anime husbando is real, He looks better that I imagined, I cannot look like an idiot in front of him' 

 She had fallen in love with his character when she first saw him show up in the manga and in the anime and she was heart broken and was left in tears when she found out he dies.

Yuuji: 'Wow he is much like he is in the anime'

He really likes him because of the way he smiles almost all the time and that he uses fire.

(Time skip) 

As they went to go and drop off the boy to his house everybody was behind (Y/N) fawning over how cool it was that Rengoku was actually there with them. To which it confused him a little as to why he was getting so many compliments

Gojo: "Now shall we grab some food?"

(Y/N)'s eyes had lit up when he had heard that there was gonna be food 

"Steak" 

"Sushi"

"SWEET POTATOES" (I think that is what Rengoku's favorite food is)

Gojo : Leave it to me! And you, Megumi?

Megumi ignored him while swiping on his phone  

"Okay lets go" Gojo said leaving Megumi behind 

As they were walking to get some food Nobara decided to ask 

"Rengoku?"

"YES WHAT IS IT?"

"Uh... C-Can I wear your cape?" She asked while blushing 

"OK THEN" he replied as he took off his cape and put it over her shoulder

'It is really warm and it smells nice'  She thought, the others were pouting because they were about to ask the same thing 

She then looks at your hand and decides to grab it, to which you show no reaction to 

'Im gonna make sure nothing bad happens to you'  she thought

Well that is it for my first chapter and I hope you enjoyed it. Again this is my first time doing this so let me know if I did anything wrong.