Fight me, Become a Demon

Prolouge

All artwork used in this story is my own, you can find more of my artwork on Instagram (account: Sugarbreadcat)
Before we start I have to give a content warning if you did not see the one in the description of the story.
WARNING: this is a Demon Slayer crossover featuring a DEMON main character, there will be descriptions of blood, mild swearing, might MIGHT have some suggestive content (I don't know at the moment but I'll update this when I decide to add this or not), cannibalism (idk if it counts when it's a demon but there is eating of humans in this book), death, and torture. Reader discretion is advised.

    A grey hand slides open a thin shoji door, the pink nails lightly digging into the wood as the light from the moon high in the sky cast a shadow. Blue fingers release the door as the woman steps inside the mansion. Her shoulders were relaxed and her footfalls were nearly silent, only the light clicking of the pink beads of her ankle bracelets could be heard by the supernatural. The messy pink hair that barely laid an inch below her ears slightly moved as she closed the door behind her, plunging the hall into complete darkness once more. The only light source left were two yellow glowing eyes overlaying a background of blue cracked glass. In place of pupils was a kanji inscription, Upper Three, which added to the eerie atmosphere.

The hallway stretched almost impossible long, a testament to the wealth that the owner hoarded. Painting scrolls decorated the walls every few yards, images of tranquil gardens with beautiful women and domestic pets occupying the space. The paintings were easily identifiable as expensive, but the rest of the hallway was bare. However, she wasn't sent here to steal wealth. She was here to obtain information by any means necessary.

Continuing down the hallway, she came across a door that was slightly open. There was a man inside, he was in deep sleep with his back was turned to the door. He did not move in his futon as the woman silently slid the door open further, silently stepping into his room. His breathing remained even as she approached him as she blankly stared down at his vulnerable form. She lifted her foot, slamming it down on the man's wrist. Flesh and bone separated until the man's hand was severed from his arm. The man woke up with a bloodcurdling scream, the pain and terror coursing through him as he tried to figure out why he was in pain. The fog left by sleep quickly left his brain as he looked on in horror as his hand lay severed from his arm, a foot standing in the gap where his wrist should have been. He snapped his head up in shock, eyes racing up the body of the woman in front of him.

The man opened his mouth to let out another scream at the monster but he didn't get to. Instead, a hand closed around his windpipe, cutting off his breath and sound all at once.

"Shut. Up," the woman growled, hand squeezing tighter as each word passed through her lips. Her eyes narrowed as she watched the man struggle for breath, his legs kicked wildly in hopes that he could get the woman off of him. The arm that still had a hand attached was clawing her wrist. His face was slowly turning blue as the lack of air was getting to him, the woman relaxed her grip as his movements started to slow. The man gasped for much needed air as the color slowly returned to his face. The man took a few more gasping breaths, wheezing as the adrenaline started to wear off and the pain from his wrist being pulverized returned. Tears gathered in the corners of his eyes as the woman watched impassively from above, her hand still wrapped around his bruising throat.

"What do... you want?" The man struggled to say in a scratchy voice. He knew that the woman threatening his life was a demon, the only thing he could hope for was that his death would be quick.

"Tell me what you know about the blue spider lily." She demanded. Her eyes stared into the man's promising death if he even tried to escape.

"I... don't know!" The man gasped, a fearful expression painting his features. A bead of sweat slid down his forehead and into his eye, causing him to squint from the sting. "My grandmother told... me stories... but she said it... wasn't real!"

"Are you sure you're telling the truth?" Even though there was a very low chance of him lying, she had to be sure. Her master had been searching for the blue spider lily for thousands of years and his mercy, while very limited, was starting to run out.

    The woman's fist shot towards the man's knee, shattering the bone on contact. She was careful with her strength as adding an extra gaping wound would lessen the time she would be able to question the man. The man's back arched as he shrieked in pain, the tears at the edge of his eyes ran down his face. He tried to scoot himself backwards, anything to get away from the demon. This action was proved futile as the woman crouched on his chest.

    "I DON'T KNOW!! I SWEAR I DON'T KNOW!!!" He sobbed, his face turned to the side as he couldn't look her in the eye.

Gritting her teeth in frustration, the sound of her canines nanshing together made the man flinch. His anxiety skyrocketed as he realized he wasn't getting out of this situation with a painless death. Her hand clenched into a fist and she delivered a straight punch to his throat. She didn't care anymore as this was another dead end and a now a meal. The force separated the head from the body, blood spraying from the stump. It coated her hands and rather than feeling guilty the woman felt hungry. She ripped flesh from the body, stuffing it into her mouth and working to sate her desire for blood. As she consumed she felt frustrated at the lack of information, finishing her meal off she wiped her mouth as her eyes scanned the room. The glowing gold hues settled on a bookshelf that was stuffed to the brim with books.

    She stood up and made her way over, glancing at the titles. She traced her blooded fingers over the spines, nothing caught her attention. Turning away from the bookshelf, she was about to leave the mansion until faint whispers suddenly made her still.

Ah, my lovely Lady,

The noble and beautiful flower of evil,

You are the most beautiful, number one in this world.

    She slowly turned towards the bookshelf again, there was an ornate mirror fixed to the wall next to it that wasn't there before. The glass cast off a faint glow, the inside of the mirror looking foggy and dark. It was as if a completely different room was inside it, the walls instead looked to be stone but she couldn't be sure as there was an excess amount of fog blocking the rest of the room inside from view. It was completely different to the one the woman was standing in.

ーMirror, mirror on the wall, who's the most...

ーFor thee, guided by the Mirror of Darkness,

Follow thy heart and take the hand of the one reflected in the mirror.

    After the mirror whispered these words a hand materialized in the fog, the hand slowly unfurled into a welcoming gesture. There was space on the hand for her own. This brought back fuzzy images of a woman with black hair, her hand held in the same position and waiting for her to take it.

Flames that turn even stars into ashes,

Ice that imprisons even time,

Great tree that swallows even the sky,

Don't be afraid of the power of darkness,

    The woman stepped forward hesitantly. The images of the black haired woman lingered in her mind and she curiously crept towards the mirror, uneasy but unable to tear herself away from the faceless woman in her distorted memory.

Come now, show your power.

Mine, theirs, and yours,

There's only little time left for us.

    Now in front of the mirror, she takes the hand. It pulls her to the mirror as her vision fades to black.

Do not let go of that hand, at all costs.