You shot up awake, and your sister didn't know what to do. You were sweating a lot, and you fell out of bed. You struggled to stand, but once you got on your feet, you decided to leave your room. The pain went right through you, but you felt something that wasn't right. You needed to warn the others before it was too late. You slid open the door and looked around to see where you were at.

"Y/n?" A butterfly girl said as you were barely able to hold yourself up.

Your fingertips were purple, and she could see your breath. In the hot weather.

"Where is Tanjiro?" You asked as you grabbed your sword that was next to the door.

"He's down the hall. You need to stop. You are too sick to move around like this," she said as you looked down at her.

"When have I ever been well?" You asked as you took your robe off, revealing a thinner kimono.

"You look dead!" The girl said as you smiled.

"Don't worry, my time is coming," you said as you went down the hall.

You slid the door open, and Tanjiro was reading medical books on every condition out there. He didn't make it far, and you fell to your knees, feeling weak. The doubt of you hitting the floor woke Tanjiro up as well as Inosuke, Tokito, Zenitsu, and Inosuke.

"Y/n?!" Tanjiro yelled, shocked as you nodded.

"Demon, in the forest. I feel it. It's coming. I saw it, I just wanted some alone time," you weakly said.

"Y/n, you should be in bed!" Tanjiro said as you were breathing heavily.

"We got the demon, Y/n," Inosuke said as Genya looked at you shocked.

"Y/n?" He asked softly.

"There is another demon. I... I know there is," you said as you tried getting up.

"Well, um, there is. You have a sister. She turned into a demon to save you, but she just prolonged it," Tanjiro said.

"I don't have a family. Everyone is gone," you stated.

"Not necessarily. Do you want to talk to her?" He asked softly.

"He's telling the truth. She was inside your body this whole time. Since you were ten. You never noticed her because she wanted you to have a life of your own. She said your parents were terrible and they were trying to kill you because you were sick all the time," Genya explained, "I know I haven't been kind to you, and for what it's worth I'm sorry. Most of the time, I thought you were faking it. I don't deserve your forgiveness, but I want to let you know I wanted you to be stronger. I thought you weren't trying hard enough, I was wrong, I'm glad I was," he said as he helped you up, and you saw a demon head poking out of your room.

"I'm not alone?" You asked.

"You never were. She made sure of that," Genya said as he took you back to your room.

"Hi," you said as she smiled.

"Hi, I'm Sarah. You don't remember me, and it's okay. They hurt you badly before I could stop them," she said weakly.

"It's okay. Is it just the two of us?" You asked.

"Yeah, well soon it will be just me, I guess," she said weakly.

"We need to catch up before I fall asleep again," you said as she nodded.

"We do, little sister. we should get your friends too," she said.

You tried to stay awake, but it didn't take long for you to pass out. Your sister started crying, knowing that was the last time she was ever going to talk to you again. It wasn't fair. She chose to be a demon to save you, so why couldn't she save you from dying? She loved you with all of her heart. It just wasn't fair.

It was dark now, and everyone was just waiting for you to pass now. You were so pale that even snow looked darker compared to your skin. You, however, were still fighting to live. It was hard for them to accept, but your body was dying.

"The area is silent," Tokito said as Inosuke went outside.

"Feel it?" Tanjiro asked as he could smell something off.

"A demon?" Genya said as he got out his gun.

"Why here?" Zenitsu asked, terrified.

Inosuke was thrown back into the house, making him laugh.

"Demon!" He yelled, making your sister get up and growl.

"I'll be back, my little sister, I won't let this demon kill you," she said as they started fighting the demon.

The demon was strong they were trying to find openings, but the demon multiplied every time it was killed.

"Come here, you little bastard!" The demon laughed as he grabbed Tokito, then Tanjiro.

"You lose," he smirked as the others were lying on the ground in agony by the duplicates of himself.

You heard screaming and yelling outside, so you decided to head out with your sword in hand even though you had no chance of winning in this state. You followed the blood trails and the fallen trees to see several demons trying to kill your friends and torture them.

"Let... them go!" You yelled even though you could barely stand.

"No!" Sarah screamed as a demon quickly came over to you and took your sword, then stabbed you in the chest.

"No!" Your sister screamed as you died right there.

Everyone looked horrified. You even made it outside. Tears ran down her face, making the demon laugh.

"You call yourself a demon? You cry when humans die," he chuckled.

"She was my sister!" She screamed as Nezuko was facing the same brutal torture.

"Let them go!" Tanjiro yelled.

"You are going to be a nice snack!" He hissed as he was about to take a bite.

You slowly grabbed your sword and pulled it out. You fell to the ground but slowly got up.

"Strange things have happened here. I am not supposed to be alive, but of course, that's what my parents told me," you said as needles that were in your skull from birth made their way out of your skull.

Your arm and leg burst into flames while your breath could be seen in the heat of the night. A noose appeared around your neck as well as a knife that was in your chest. Your clothes were soaked with water, and a pool was forming from under your feet. Water dripped from your mouth as your nails started to grow longer. A dark ora appeared around you, and it was thicker than any fog.

"Let them go," you ordered as you didn't look at them. Your body grew taller, and black lines appeared on your body with golf branches extending from them.

"You don't tell me what to you, little girl!" He hissed as you sprouted wings like that of a bat.

"Oh, but I do, and I am... you know my sister turned into a demon to save me, but the truth always was my body was trying to kill her. She thought she was saving me, but she was wrong. I was feeding off of her without even knowing it. But after I got strong enough, I didn't need her anymore. The day she died, I died too, and she became a monster because of her. She thought she killed our parents, but it was me. I had enough of being killed," you said as you opened your eyes and sent the main body flying

"Light art Seventh form, Morning glory blade dance!" You yelled as you unleashed the attack, making everyone speechless.

"Light art, eighth form, stargazer!" You yelled as it looked like hundreds of stars came from the sky and started hitting the demon.

"You are supposed to be sick and weak!" The demon yelled as you looked down at him.

"I was never weak when I died, merely overwhelmed to the point I forgot I even had the strength to fight. But my sister sacrificed so much for me, and by her unwillingness to leave me, she gave me back the memories I lost," you said as the other bodies were going after you but you quickly defeated them with a single slash. The demon tried running, but you took off after him and started going full force on the demon, taking out trees in your wake. Your style of fighting was so much brighter than it ever was.

"Are you? Are you coming to the tree? I strung up a man, it's said he murdered three," you said as the sun started to rise.

"Don't kill me, please," he begged as you smiled a little.

"I could have finished you off a long time ago, but you turned my sister into a monster, but I should thank you. If it wasn't for you, I would be dead because of everything they did to me. They only wanted one boy and one girl or two girls. I was the weakest, and yet I refused to die because my sister needed me more than anyone else ever did," you said as you quickly killed him.

The sun started to rise, and your sister was running to you.

"Y/n! Get out of the way of the sun! You will die if you don't!" Your sister screamed as the sunlight was on her heels, so you quickly went to her and threw her deep into the woods.

The sun touched your skin, making you scream in agony as you started to burn.

"Y/n!" Tanjiro yelled.

"My sister is in the woods! Save her!" You yelled as you burst into flames, making him cover you the best he could.

Genya took off his shirt and tried to cover you up, but the sun had already done its damage to your skin. At first, Tanjiro thought your bones were left, but to his surprise, you were still there, just all your demonic energy was gone. You had passed out but shot up quickly and started to vomit.

Nails, rocks, needles, coins, and glass were coming out of your body violently. Blood was mixed into it all, and everyone was shocked seeing all the stuff come out of your body. It ended up being a good-sized pile that was bigger than Tanjiros' hands put together that ended up out of your body. Some of the metal was rusted, and once you were done, you sat up and sighed.

"I have the worst hangover. Tanjiro.. guys, there is a demon in the woods, and I mean a big one! Wait, where are we? Oh no, did I pass out again? What the heck is all this?" You asked, picking up some of the blood-covered stuff that was in your body.

"You're okay!" Tanjiro said as he hugged you and started crying.

"Did I pass out in the middle of a battle or something?" You asked as Genya hugged you, which confused you.

"Hold on! I'm still mad at you for pushing me into the water!" You growled as you saw your sister on the edge of the woods.

"Demon!" You yelled as your sister laughed.

"Forgot me already?" She asked as you looked at her for a food-long moment.

"Sarah?" You asked as your memories started to flood back to you.

Your parents were horrible to you, and the only person who cared if you lived was your twin who took care of you in secret instead of letting you die.

"I was a demon for a second," you said as she smiled.

"I guess when I was near death and became a demon you got some of the blood too but since you were so weak it kept you alive I did the same but you got overloaded by my presence. I may have stopped you from healing this whole time. I don't know anymore. You may have used all your demon powers up as well," your sister said as Tokito and Inosuke saw you alive.

"I thought you were supposed to be dead!" Inosuke yelled.

"I did! But because I was part demon, I lived, I guess... I need a nap," you said as Tokito smiled as he saw your sister alive and in the shadows.

"Well, let's go! We got a box to build a demon a house to fix up!" Tanjiro said as Zenitsu sighed.

"I want a nap too!" He whined.