(Readers POV)

I am running through a forest at the dead of night. I jumped up past the trees and saw some nearby railroad tracks. I heard a loud engine noise, making me look over. I saw a bright light coming towards me. I saw a train going past me.

(Y/N): The train...

I started to quickly run, chasing the train. After about an hour of chasing the train, I saw it start to turn flesh.

(Y/N): So that dream guy finally decided to try and to kill them.

I looked ahead and saw flesh tentacles about to attack at something, but I saw a boy wearing a green coat slash them apart. I just watched the fight from afar, not interfering. Eventually a boy wearing a boar's head started to help as well, slashing at the demon train.

(Y/N): Training demon slayers? They show great potential. I can see why Lord Muzan wants them dead.

The two eventually were able to break through and slash the demon's neck, making the train derail and crash into the ground. A bunch of dust came up from the impact. I stopped running and waited for the dust to settle. When it did, I found the body of the demon that failed his mission. I scoffed as I quickly went over at his dissolving corpse.

(Y/N): How could you fail? You had them right where you wanted them and you still failed? Such a failure for a demon.

All that is left is his eye. I raised my foot and crushed the eye under my foot. I chuckled to myself as I looked over and saw the boy with the green coat on the ground. A woman with fiery hair is next to him, helping him regulate his breathing. She looked over and saw me, making her ready her blade.

Rengoku: Another demon!

(Y/N): That surely is one way to greet someone you just met.

Rengoku: I do not care if I greet you the wrong way!

(Y/N): We have a feisty woman here. I can tell... You are a Hashira. I was sent to kill you, so no hard feelings, ok?

Rengoku: So you came here to take my life! I will not let you easily take it!

I looked over at the boy on the ground and noticed a pair of earrings on him. I felt my blood start to boil. No, not my blood, but Lord Muzan's blood start to boil. I have no choice but to kill him, even if he can't defend himself in his current state. The woman noticed me staring at the boy and took a step to the side to get more in front of him.

Rengoku: He has nothing to do with this! Don't you dare think about attacking a defenseless person!

(Y/N): My my, must you shout everything you say? You don't have to put so much passion into everything you know.

Rengoku: Yes!

I blinked a bit, looking at her. I smirked as I got ready to fight her. I jumped forward, getting right in front of her. I tried to punch her, but she blocked my fist with her blade. She slashed her blade up, cutting through my arm. I jumped back and healed my arm back together.

(Y/N): You are stronger than I thought. May I know the name of this Hashira?

Rengoku: My name is Kyojura Rengoku! The Flame Hashira! And I will be the one to kill you!

(Y/N): I am the Upper Rank demon known as (Y/N)!

I smiled at her as I cracked my knuckles. It's been forever since I fought someone with such confidence. I'm going to have so much fun with this! I ran at Rengoku and tried to punch her again. She blocked it with her blade, but I quickly punched her with my other hand, knocking her back. She kicked off the ground and came right at me again. I jumped back, but she slashed at my chest, leaving a cut. I began to punch the air, sending a powerful shockwave.

(Y/N): Take this!

Rengoku got hit by the shockwave, getting knocked back. I kept sending more and more shockwaves at her. She tried to block them, but had some trouble.

(Y/N): Come on! You can do better than that, right?!

My body healed the cut on my chest as I ran over at Rengoku. She dodged my punch and tried to slash at my neck. I quickly turned my body, making her blade cut down into my chest. This is the most damage a Hashira has done to me in a long time. I punched Rengoku, knocking her away. I grabbed onto the blade and pulled it out.

(Y/N): You demon hunters. Using these swords as crutches. Can you not fight me without giving yourself an advantage? Absolutely disgusting!

Rengoku: You think being a demon isn't an advantage?

I heard some movement. I looked over and saw the boy with the green coat trying to get up and look at me.

Rengoku: My young Kamado! Don't move!

Tanjiro: You... We humans are fighting you demons at night... Your territory... Don't try to say... What is and isn't fair!

I looked down at the blade. I scoffed as I threw it at Rengoku, making it land on the ground next to her.

(Y/N): Fine. I guess I'll just have to stop holding back then!

Rengoku quickly picked up her blade. She tightly gripped onto her blade as we started to run at each other. I got in front of her and tried to punch her, but she swung her blade at my fist, deflecting my attack. She started to swing her sword at me wildly, putting me on the defensive. She raised the blade over her head and swung down, making me use my arm to block it. The blade cut into my arm half way. I tried to deflect it, but she kept putting force down. A bunch of force came out as a result. She managed to cut through my arms, cutting them off. I quickly spun around and kicked her in the side of the chest. I can feel her ribs break from the kick as she was sent away. I regrew my arms and smiled.

(Y/N): What's wrong? Can't keep up?

I smiled as I jumped up and started to fall at Rengoku. I got ready to kick her again, but she jumped back, making me hit the ground. I saw Rengoku try to slash at me, but I dodged the blade and punched her in the face, sending her back and making her crash into the fallen train.

(Y/N): I can feel it. Your body is beginning to fail you.

She started to take some deep breaths as blood flowed down on her face.

(Y/N): I like fighting you. You put everything into every single swing. I would love it if you became a fighting partner... Become a demon.

Rengoku: What?

(Y/N): All the wounds you have inflicted onto me have already healed, but yours... I can't say the same. If you became a demon, your fatal injuries would heal in an instant. You could live for a hundred, no, a thousand years and not lose a single ounce of strength. I think-

Rengoku: Enough! I won't become a demon!

I got mad that I was interrupted.

(Y/N): Why not?! It would solve all of your problems! Don't you fear getting old and losing that strength of yours?! Why wouldn't you get rid of the weaknesses of your human body?!

Rengoku: ...Growing old and dying is what gives beauty to the fleeting span of a human life. It is precisely because we age and die, that our lives are unbearably valuable and noble. Strength is not a word that means much in regards to the flesh.

She got into a stance and readied herself. Her grip on her sword became as tight as a vice as I can feel a strong heat coming from her.

(Y/N): With those injuries... How could you still want to move?!

She smiled at me with a determined look in her eye.

Rengoku: Set your heart ablaze!

She dashed at me and got ready to attack me. I put my arms up and got ready to block her attack. With her injuries, this attack won't do much. I saw her blade swiftly cut through my arms completely. I felt a burning sensation going through my arms.

(Y/N): Guh!

I quickly jumped away, but Rengoku kept running at me. Has she gotten stronger? How could she stay moving like this?! I regrew my arms and punched her in the gut. She spat out some blood, but started to swing at my neck. I felt the blade hit my neck. I felt it go deeper, getting half way through my neck.

(Y/N): You stop this right now!

Rengoku: AAAAAAAHHHHH!!!

I tried to punch her again, but she didn't budge and kept trying to cut my head off. Crap, what am I going to do?! I looked at the blade and punched it, breaking it in half. I kicked Rengoku back, making her go flying as I ripped the blade out of my neck and healed it.

(Y/N): That... Was close...

Tanjiro: No... She was so close...

Rengoku got up, continuing to stand as she readied her broken blade again.

(Y/N): Just stand down! Can't you see you're just killing yourself?! How could you do this to yourself?!

Rengoku: As long as I can move, I will do everything within my power to make sure no one gets hurts!

(Y/N): Ah!

For some reason, her words made me start to remember my life. The life I had before becoming a demon.

(Flashback)

I was in a dojo, training. I threw punch after punch in the air, sweat covering my body. I took a few deep breaths and sat down.

(Y/N): I'm going to get stronger, so I can win in this tournament.

I heard someone walking towards me. I looked behind me and saw my master walking to me.

Master: Ah, young (Y/N). My prodigy student.

I smiled as I turned to face him and bowed down.

(Y/N): It's an honor to be speaking to you.

Master: You shouldn't be training so intensely. The tournament is tonight.

(Y/N): I have to make sure that I am ready and strong.

Master: You don't want to waste energy.

(Y/N): Of course.

Master: Make sure to win and show everyone your talent.

(Y/N): I won't disappoint you.

I remember fighting in the tournament that night. I won every fight. I was getting ready for the finals. I was given some water before the match, but someone must've poisoned it. I remember fighting my opponent, but my vision started to distort and I was knocked out of the ring. I started to cough and throw up my guts as my body tried to get rid of the poison. I remember hearing people start to make fun of me, saying I was weak. I looked over to where my master was and he looked at me. He looked disappointed and turned his head to not even look at me.

(Y/N): N-No... I'm not weak. I'm strong, I know I am. Why am I not the victor?

Muzan: I can help you.

I looked over and saw a man with pale skin standing next to me.

Muzan: I can get rid of your weakness... By turning you into a demon.

I don't know why I agreed to it, but I think it was because I would become strong, and strong I became. I was turned into a demon and I killed the person that humiliated me. But I didn't stop there as I killed everyone else there. I saw my master on the ground, bleeding.

Master: (Y/N)...!

(Y/N): I'm strong master. Don't you see? Isn't this what you wanted from your prodigy student?

Before he could respond, I finished him off.

(Flashback end)

This woman... She reminds me of me before I became a demon. Someone who'd never stand down to anything or anyone. Just keeping to the goal in the mind and striving to achieve it, no matter what happens to her body.

(Y/N): Kyojura Rengoku... You are an amazing person... I'm sorry that your life will have to end here.

Even with her standing and getting ready to fight, I can see her struggling to breathe. This fight won't last much longer. I saw three people get in front of her. A blonde boy with a yellow coat that appears to be knocked out, the boy with a boar head on his head, and a girl with long black hair with orange highlights. I can tell she's a demon.

(Y/N): A demon standing with a Hashira?

These fools, I can kill them with one attack. I know that can't do a single thing to me. I looked past them and looked at Rengoku. I was about to attack her, but I saw the morning sun start to rise.

(Y/N): Shit! I gotta get out of here!

I saw Rengoku start to run at me. I punched the ground, making a huge dust cloud cover the area. I quickly ran into the woods, getting away from the sunlight as fast as possible.

(Rengoku's POV)

I watched as (Y/N) ran into the woods, escaping from the sunlight. I fell down to my knees as I struggled to even breathe. I looked back and smiled to myself as I saw people start to leave the wrecked train. I kept everyone safe. I fulfilled my duty.

Rengoku: I did it...

I heard someone moving closer to me. I looked over and saw Tanjiro walking over to me.

Tanjiro: R-Rengoku!

He got in front of me and he fell down to his knees.

Rengoku: Young Kamado... I'm glad to see you're ok.

I felt pain go through my body as the adrenaline of the fight wore off. I coughed up some blood.

Tanjiro: I-It's going to be ok! You're going to get medical attention-

Rengoku: I'm sorry... But I don't think I'm going to be able to continue my fight.

Tanjiro: N-No...

Rengoku: With my injuries, I'd be lucky to live, let alone continue being a Hashira.

Tanjiro: Please don't say that! You can't stop!

I smiled at Tanjiro and put my hand on his head.

Rengoku: I'm sorry that I couldn't tell you anything about this "Hinokami Kagura". But since I'm sure I'll be heading back home to my father, I'm sure he might know something about it.

I started to close my eyes as I felt my consciousness slipping.

(One Week Later)

I've been staying at me home, trying my best to recover from my injuries. Most of body in bandages as most of my bones are still broken from my fight. I heard a door open, making me look back and saw my little brother.

Senjuro: Sis... Are you feeling any better?

I gave him a slight smile.

Rengoku: It surely is taking its time, but I am feeling better.

He let out a sigh and walked over to me and gently hugged me.

Senjoru: I'm happy to hear that... Let me get you some water.

He let go of me and tried to get up, but I stopped him. I slowly got up and started to walk out of the room.

Rengoku: I'll get it myself.

Senjoru: S-Sis! You shouldn't be walking around!

Rengoku: I'll be fine. Trust me.

Senjoru looked at me for a moment before nodding his head. I started to feel a bit disappointed in myself. Senjoru, I'm sorry that I've failed you. I was supposed to be strong, someone you could look up to... And now I'm like this. I left the room as walked down the hallway. I saw father walking in the hallway and we walked past each other. I stopped and looked back at him.

Rengoku: Father.

He stopped and looked back at me. I can see the bottle in his hand. I took a deep breath.

Rengoku: Please... Take care of yourself.

He just stayed silent as he looked forward and kept walking forward. I started to walk again and I left the home. I walked down the street, trying to clear my mind of everything going on. I didn't even have a destination in mind, just walk.

(Hours Later)

I saw as the sun started to set.

Rengoku: I should head back home.

I began to walk back to my way home. The sun quick set as night started to darken the area. I kept walking, but I heard an extra pair of footsteps. I looked back and saw a pair of demon eyes in the darkness. I immediately recognized the eyes.

Rengoku: You!

(Y/N): I finally found you.

He stepped out and got closer to me. I didn't know what to do, but when he got in front of me, he got down on his knees.

(Y/N): I've had time to think... And I want you to strike me down.

Rengoku: What?

(Y/N): You remind me so much of myself before I became the monster I am now. I've cut down such a strong and passionate person and I just can't live with myself anymore.

He reached for something on his back and it's the broken blade from our fight and he held it towards me.

(Y/N): Please.... Get your revenge. It's only fair that you get to cut me down.

He held his head down, accepting the kind of fate that he wants me to give him. I grabbed onto the broken blade and looked at it.

(Y/N): I'm such a failure.

Rengoku: ...

I put the blade on his neck and slashed down, cutting his head off his body. His head fell down to the ground as a small smile formed on his face.

(Y/N): Thank you...

His body started to disintegrate until it completely disappeared. I stood still for a couple moments. I turned around and saw a spirit in front of me. It looks like (Y/N), but when he was a human. He walked over to me and wrapped his arms around me in a hug.

(Y/N): Don't lose that flame in your heart like I had.

His spirit quickly faded away. I started to walk forward as I looked down at the broken blade in my hand. I smiled to myself as I knew once I recover, I will continue my fight against demons.

Rengoku: I am Kyojura Rengoku, the Flame Hashira! My fight doesn't end here!