So, I absolutely just love Demon Slayer (finished the whole manga in four days and am rereading it again right now..)

So, as I always seem to do when I love a series, I made an oc. I came up with a backstory for her and even wrote most of it out throughout last night and today.
Just as a warning, again I writs the first half at like 1 am, so please ignore any errors you see... This is my first time really writing something like this in over 6 months..

So, here's her backstory:

(Spoilers to anyone who does not watch or read Kimetsu no Yaiba/Demon Slayer. So uhhh... just be careful I suppose!)

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Four years ago...

"Yuuuukiiiiiii!" I turned around, hearing my sister cry out my name. Her pale blonde hair was a mess and her emerald eyes were watery as tears streamed down her cheeks.

"Yuzuki?" I gave her a smile and walked the short distance to her. "What's wrong?"

"You- you're getting married!!! And that means you won't have any time to play with me or- or anyone else!!" She ran forward and tightly locked her arms around my waist. "I don't want you to goooo!"

I simply laughed softly at her affection and rubbed the top of her head. "Yuzu, you know I won't be far. I'll still be close enough for you to come and visit whenever you get lonely or bored. So please, don't be so upset!" She lifted her tears gaze up to meet mine, and I couldn't help but pinch her cheeks lightly.

"Pwomise?" She asked me, puffing her bottom lip out.

I reached down and lifted the girl into my arms. "Promise," I replied, poking her nose. She responded with a series of giggles and hurriedly rubbed her eyes.

Suddenly, she looked behind me and quickly hid her face behind my shoulder. Before I had a chance to turn around, I felt familiar arms wrap around my waist.

"Kaito," I greeted my fiancé and turned my head to give him a quick kiss.

Kaito was an only child, and both his parents had died of a sickness earlier that year. He was a few years older than me, but when we met it was love at first sight. I will admit, I was a bit slow to reciprocate his feelings, but soon enough we got together and were planning on getting married tomorrow. My family loved him and treated him as their own son, so it was safe to say that he was accepted as a wonderful husband for me.

Well, almost everyone completely accepted him.

"Yuck!" Yuzuki covered her face with her hands. "You two are gross!"

Kaito grinned at the young girl and ruffled her hair. "Don't be like that, Yuzu! Someday when you're older, you'll meet someone yourself and get married to them."

Yuzuki was silent for several seconds, thinking. Her eyes had mostly dried by now, and they were shifting from me to Kaito and back again. "I don't wanna get married!" She finally announced and squirmed to free herself from my grasp. I set her down and watched as she ran around the corner and into our home.

"You worried about her?" Kaito asked, likely noticing my expression as I watched her leave.

I sighed. "I just don't know how she'll be without me. We've always been together, so thinking about leaving her like this is just..."

"Yuki." I instinctively turned to my love and blushed lightly as a hand came up to brush a strand of my long, light blue hair behind my ear. "We still are going to live nearby, remember? If anything ever happens, we will be right here for her."

I nodded and glanced down to hide my reddened face. "Right. Thank you, Kaito."

He planted a kiss on my forehead. "I'm going to head inside and see if your mother needs any help with food. You should go into town and see if there are any last things you need for tomorrow."

I nodded once more and wait until he's left before turning and heading up to the town. It wasn't a long walk, and I managed to reach it in just a few minutes.

It was a small village, with just a dozen shops and businesses. Everyone knew one another, so there was never any fear in walking around by myself.

"Hey, have you seen or heard from the Sato family?"

"I haven't..? Why do you ask?"

"Well... I just haven't heard from them recently. I just hope everything is alright with them."

Sato? I turned my head slightly in the direction of the two speaking. Hayama Sato was my best friend, and while it was true I hadn't seen her in a while, she had said that she wanted to surprise me on my wedding day- tomorrow. I wasn't too worried, but decided I'd just go and check on her (and maybe snatch a peek at her gift for me, who knows?)

I snickered quietly to myself and pressed on, an extra bounce in my step.

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"Bye, Yuki! And congrats on your wedding tomorrow!"

I waved bye to the shopkeeper and walked outside, wearing a lavender flower I'd bought from him in my hair. The sun was quickly going down and the sky was darkening fast. I gathered all of my belongings and started going back to my home, memories of my childhood resurfacing in my mind.

When I was just a little girl, my grandfather would entertain me with stories of demons who hurt good people. They would only come out at nighttime, and could do almost anything possible.

I can clearly remember sitting eagerly and staring at him while he introduced Slayers, the heroes who would fight against the beasts. The Slayers were mere humans, and yet fought with such bravery that anyone would be a fool not to admire them.

I smiled and let out a chuckle. I was so childish back then, believing everything I heard. I had actually thought that those tales were true, but as I matured I soon realized there was no such thing.

My house was up ahead, and I hurried inside. Kaito and Yuzuki greeted me with a hug and my parents brought me over to enjoy our dinner.

The food was delicious, my mother having made an extra large serving of my favorite dish, asari miso soup.

After an hour, we all finished and put our dishes away to be cleaned later. Mother sent Yuzuki and me to bed ("you have a big day tomorrow, you should get some rest while you can"), while Kaito stayed up to help my parents and speak with them for a little bit longer.

"Yuki?" My sister whispered from the other side of the room in her bed. "Once you're married, will you promise to never forget about me?"

I blinked at her question. "Of course, Yuzu. I promise. Besides, how could I forget someone as adorable and amazing as you?"

Yuzu let out a quiet laugh before going silent. Her breathing evened out, signaling she was asleep.

The whole house was dark and not a sound could be heard. Even still, I found myself unable to rest.

Perhaps it is just my excitement for tomorrow?

I sat up, finally giving up on trying to fall asleep. Immediately an image of Hayama came to my mind. That's right! I had completely forgotten about going to visit her!

I mentally kicked myself but let out a sigh; there was nothing I could really do at this point. Besides, I'd see her again tomorrow.

Go to her now.

I felt a sudden urge to go and meet my friend. I didn't know why, since she was asleep and I'd see her tomorrow anyway.

Go to her now!

Confused, I stepped out of bed and went to the door to exit my room. Perhaps I just needed water? Wherever the reason I kept getting these feelings, I wanted them to stop. Yes, I'd missed seeing my friend, but-

Go to her NOW!

A sense of fear overcame my body, and without even thinking I ran out of my home and up the hill to where Hayama lived. I could hear the bushes rustling near my home, but there was nothing there.

Why? Why was I suddenly so afraid? She was fine!

As I ran, my grandfather's warnings came back to me: "Yuki, when it gets dark outside, you must make sure to stay inside and close all doors. The monsters only come out at night, and they love preying on unsuspecting little girls."

"Not now, Grandpa!" I yelled out loud, trying to get the memory out of my head.

I continued my race, finally seeing Hayama's home.

The door was open.

I slowed my pace and let myself catch my breath, only to immediately be met by a rotting stench. I gasped out and covered my nose with my hands in a poor effort to block out the awful smell while I tried to regain my air.

"Sato-san?" I called out once I could finally breathe again. "Hayama-chan?" I went forward when I heard no response from inside, only to stop at the entrance to their home.

This is wrong, they're just sleeping. I shouldn't just walk in on them all like this...

Nevertheless, I gulped and nudged the door open more.

Blood was the first thing I saw.

Smeared all along the walls and splattered across the floor, dried blood was left in a horrifying stain across every surface. Torn pieces of clothing lay on the ground, covered in the same red liquid.

I was petrified in fear as I stared at the scene before me.

"H-Hayama-chan?" I squeaked out, finally managing to gain up enough courage to carefully walk inside. "Hayama, if this is what you had planned for tomorrow, it isn't funny!" I made my way towards her room, the disgusting smell worsening with every step forward. "Hayama-"

I found her on the floor of her room, the whole left side of her face gone. Blood was soaked completely over clothes and dyed her once-beautiful gold hair crimson.

Bile rose in my throat, and I could feel my head becoming light. I needed to get out of here. I just needed to go back to my home and wake up and everything will be fine! I'll have my wedding, and Hayama will come and give me a hug and congratulate me on everything. Everyone will be there and we'll all be safe and happy! Afterwards, Kaito and I will leave and live together, and have our own family. Yuzu will be an amazing aunt, and will protect our children and love them as her own.

Everything will be alright, if I can just get back home and wake up from this horrible nightmare.

I sprinted back home, and my desperate attempt to reason with myself did nothing to overcome the dread and fear I felt. What was even happening? What was-

The lights to my house were on. I smiled to myself and relaxed. Everything's fine, see? They probably saw that I wasn't in my bed and were trying to find me. And that scene I saw back with Hayama...

That didn't matter, it was simply my eyes playing tricks with me. Relaxed, I went in and pushed the front door open.

"Sorry I was gone, but I'm here-"

All words escaped my throat at the scene before me. Blood filled the room, still fresh and running down the walls. The lighting only seemed to make this nightmare worse, as I could now very clearly see the bright red of stains and handprints from my family.

My mother was laying in a corner of the room, and I hurriedly went to her side.

"Mom?" I gasped out. No response. "Mom?!" I turned her over onto her back, noticing a deep gash running from her shoulder down to her waist. Blood seeped out of the wound as I moved her, but other than that she was completely still.

She was dead.

A sob escaped my throat as I cradled her head and hugged it to my chest. "I'm sorry... I'm sorry for everything... I'm sorry for leaving you..." I pulled back and gazed at her motionless face once more before gently brushing her snowy blue hair to the side of her head. "I'm sorry..."

I heard a growl from the direction of my room, and I lifted my head up instantly at the sound.

Yuzu!

Leaving my deceased mother behind, I jumped up and ran to my room. There, my forest-colored eyes widened even more at what was happening in front of me.

There was a creature- a monster- leaning over the lifeless bodies of both Kaito and Yuzuki. From what I could see, Kaito was laying over the girl, almost as if protecting her from this beast. His night-colored hair was a mess, and I could do nothing but stare in horror as the monster leaned down and took a large portion of his neck into its mouth.

I quickly covered my mouth, feeling like I was going to be sick again. My eyesight was getting blurry and I was feeling dizzy...

The monster swung its head in my direction, scarlet pupils dilating at the sight of me. It let out a low chuckle, blood and bits of flesh falling from its mouth. "Well, what a surprise! A new person to add to my feast!" It crawled towards me, abandoning the two others it was just preying upon.

I stood frozen in place. It was like I had completely forgotten how to move- how to breathe. The monster crawled closer still, and I was completely helpless against it. I was frozen in place as it suddenly leapt at me.

A force pushed me to the side, and I fell on the ground. I regained my sight, only to see another person standing behind the beast. His sword was out and red with the blood of the monster.

The monster, on the other hand, had its left arm completely gone, yet it didn't seem the least bit worried.

"So, a Slayer really did decide to come, after all!" It let out a laugh and regrew its arm in just a full second. "I had heard all about puny mortals like you, but never once have I encountered one! Oh, this is going to be fun being able to feast upon you!" It turned around, finally making eye contact with the man.

The man glanced at me for just a moment, scanning me for any injuries. Then, he readied his blade and focused again on the creature before him.

"Water Breathing- First Form: Water Surface Slash." Water formed all around his blade, creating a powerful force that was aiming at the monster while he swung the sword.

The beast leapt back and frowned to itself, no doubt thinking of how to defeat its opponent. It locked gazes once more with the man and moved its arm to stab at him with pointed claws.

"Water Breathing- Seventh Form: Piercing Rain Drop." Water once again collected on the man's sword as he thrust it forward. The blade cut through the creature's hand and went right through its chest. He pulled his blade out and changed his stance once again. "Water Breathing- Fourth Form: Striking Tide."

The monster was in shock from the onslaught of attacks and had no time to prepare or dodge the man's blade as he slashed across its body multiple times before finally dragging the sword across the monster's neck. In a single strike, the head flew off and landed on the ground a few meters away.

"How... how could I have lost? This isn't fair! I ate so many humans! How could I have lost to you?!" The monster spat at the man in hatred as it turned to dust just seconds later.

The man finally turned to me and came close, sheathing his sword. "Are you hurt?" He asked, leaning down and offering me his hand. He eyed the blood stains covering my body, likely assuming they were my own. After I made no movement, he sat down so he was eye-level with me.

"I...." I began but stopped as everything finally caught up to me. The things I saw, the fear I had... now that the danger was gone, I was overwhelmed with other emotions. Large, wet tears formed in my eyes and I hurried to hug the man who had saved me from death. "It's my fault! I should've stayed here with them! Then- then I could be with Mom and Dad and Yuzu and Kaito!"

Kaito... More tears fell as I thought of the beautiful man's smiling face and his love for me. An ugly wail escaped my throat and I buried my face deeper into the man's asymmetric haori.

"We were going to get married tomorrow..." I gasped out, and felt the man stiffen slightly as he heard that. "I should've been the one to die in his place..."

"Don't say such things," the man commanded suddenly. His voice was even and calming, yet laced with concern. It almost sounded as if he's gone through this exact same struggle...

After a few minutes I pulled myself away and looked at the man in front of me. His eyes were a dark blue, like waters of the deepest ocean. His black hair was a mess, sticking out everywhere and partially covering the right side of his face. He didn't seem to be much older than me.

"Wh- who are you?" I breathed, confusion returning to me. Why would this man risk his life to save me- he didn't seem any older than eighteen. It just didn't make sense.

The man was silent for several seconds, thinking of how to answer. "I am a Hashira, one of the strongest Demon Slayers. That monster you saw earlier was a Demon. They scour the land looking for humans to consume." He pursed his lips. "That is unfortunately what let to your family's demise."

"N-no!" I grabbed onto his arms. "That isn't fair! This doesn't make sense! Why do they do this?! Why-y-y-y..." I broke down again, my head falling limp into the man's chest.

The man placed his hands onto my shoulders and pushed me back. "If you want to stop all of this, then let that vengeance fuel your desire and become a Demon Slayer yourself. I can feel that you have what it takes to be able to fight them and win."

Become... a Demon Slayer?

I blinked at him in confused silence, before he finally stood up and lifted me to my feet. "I had heard reports of people coming up missing in this area, so I came by to check it out. It seems I managed to defeat it before you got attacked." I blindly followed the man and let him lead me back outside my home. He put his arm up, blocking the view of my mother as we passed her. There was nothing I could do.

The man brought me into town and bought me a room in one of the two small inns. "Stay here for the night, and tomorrow head east. There are sword experts in that direction, and they will be able to teach you everything if you want to ever become a Slayer."

His ocean eyes met my emerald ones, and he turned away without another word and left.

I went to my room, numb and tired. It was definitely past midnight, but despite that and my exhaustion, I was too scared to sleep. Memories of what had happened over the past few hours haunted my mind, and finally I fell onto the bed and cried, hugging a pillow to my chest as I tried to comfort myself.

And thus marked the start of my new life.

Aaaaand that's it..!
I was planning on also adding a bit of her training here, since that still counts as her backstory (not really, but kinda..) but this was getting pretty long already.

Anyway uhmmmm I guess that's pretty much all of it..! Maybe I'll do some more chapters of this little story thing, but only if people will actually read them.

With all that aside, here's my oc, Yuki Asatenshi. She controls the Breath of Winter, inspired by Tomioka's own Breath of Water.

(Please ignore the move names, I literally just wrote the first thing that came to my mind and yeah..)

And here's her and Giyuu several years after this story (when she's finally a Demon Slayer and meets him again..

(Ignore poses + Giyuu's hand, I can't draw..)