A supernatural past

Karma was on top of the house staring at the stars in the night sky. He was so deep in thought that he didn't notice the arrival of a cute black cat beside him.

The cat looked at Karma before it let out a cute 'meaw' which awoke Karma from his daze. He turned his head to look at the cute cat who was cutely scratching it's small head with it's cute little claws. Karma couldn't help himself and involuntarily said " cute ".

Karma slowly tried to stretch his hand to pet the cat's head. It looked at the stretched hand of Karma slowly moving towards it's head trying to pet itself before tilting it's cute head and openings it's mouth, " for a cold-hearted assasin you seem quite warm at this moment Nyah ". The hand snaking towards the cat retreated in embarrassment.

The cat soon transformed into a beautiful young woman with a voluptuous figure, long black hair with split bangs, and hazel-gold eyes with cat-like pupils and cat ears and two cat tails. Her attire consists of a black kimono, a yellow obi, a set of golden beads, and an ornately detailed headband. The kimono features a red interior and it is open at her shoulders, giving view to her large breasts which rival those of Rias and Akeno in terms of size. Her name is Kuroka Toujou an SS rank criminal of the underworld and an ultimate class nekoshou.

" I'm quite curious of why would an SS rank criminal come to my house " asked Karma while looking for answers from Kuroka though he already has some guesses.

" The same could be asked of you though, what is an SS rank criminal like you doing in the peerage of Lucifer's sister nyah " Kuroka asked Karma with a serious expression while releasing her magic pressure on him. " What has it got to do with you? " asked Karma while mischievously smiling at Kuroka. " Depending on your Answer, I might eliminate you ".

Karma reassessed Kuroka once more before calmly looking at Kuroka like he wasn't intimidated by her magic pressure at all. He said " if you're worried about me harming Shirone, then you don't have to because I'll never think about harming her even in my dreams " he finished with a small smile.

Kuroka was extremely shocked after hearing his answer " y-you how do you know her real name? " asked Kuroka coldly. She was sure that her real name was only known by the Gremorys and herself and everyone else who knew her real name are dead so she didn't know where he came to know of her name. ( It's for the sake of the plot and pretty sure I'm probably right about her real name only being known by her close friends and even Issei didn't know at the beginning )

Karma looked at the frowning face of Kuroka and said with a reminiscent smile " it's quite sad that you don't remember me though I understand why, even I won't recognise myself in my current looks. By the way your ears are as charming as always Sister Kuroka "

Kuroka widened her eyes before she slowly said while stuttering " how yo-you should have been d-dead so h-how? AKIRAAA " ( It's Akira. Sorry to all the Arima fans but he wouldn't fit for the character of my MC you'll know why ) she flew into the arms of Karma while crying in his chest.

-------FLASHBACK-------

A small girl with approximately ten years of age with black hair and cat ears and tail was lying on a table with her limbs strapped and small tubes with black liquid was being injected in her veins making her scream. This was little Kuroka. The pain lasted for quite a while before stopping.

Afterwards two scientists entered inside the room and checked some equipments before saying " it's failed again. Collect the date and reschedule for her next experiment also prepare the epuipment for the boy today will be the day ".

Kuroka was dragged to a room by a researcher before he left her there and locked the room. " KUROKA-NII-CHAN I was s-so s-scared " a little girl approximately seven years of age with white hair and cat ears and tail said while hugging and crying in Kuroka's arms. This was Shirone, Kuroka's little sister. " See I told you that sister Kuroka is strong and nothing will happen to her. Sigh I wish my stupid brother was as brave as her " This was Silvia a small girl with silver hair and cute appearance, the same same age as Shirone. " B-but Silvia you d-don't understand they're mon-monsters you don't know the pain they cause me h-how can I not be s-scared? I don't want to be here anymore I w-wan't to go back " This was Akira, a small, thin and weak looking boy with black hair and blue eyes. He was nine years old and the adopted brother of Silvia.

Akira was left at the orphanage at his birth and since then he has been there. He was a smart and bright kid who was loved by everyone in the orphanage and had many friends. When he was seven years old, Silvia was brought into the orphanage along with some other kids by the police. She was the exact opposite of Akira, while he was cheerful and big brother type, Silvia was quite and aloof. She would often cry when she was alone and was once caught crying by Akira. Akira being the cheerful innocent kid he was tried to talk to her. After months of convincing her, he got her to open up a little to him. Later he learned that Silvia was sold to human traffickers by his own father because he didn't believe that she was his child due to her hair colour. Akira who didn't have any family since the beginning couldn't understand what it's like to be despised by their own parents since he's always been loved in the orphanage. So he decided to take Silvia as his little sister. He told her that with him she'll never be alone and he will be his family always.

Silvia was really touched hearing Akira's claim and was really happy. Being the child she was, she easily accepted him being her big brother. Since then she slowly started to open up to everyone and quickly became popular in the orphanage and was known as the ' tail of Akira ' by all. While being smart and acting cute, two years passed by and Akira was nine years old while Silvia was seven and their bond was as strong as always.

This was the time when someone came to adopt both of them together. Many people had tried to adopt either Akira or Silvia but they both wanted to be adopted together which no one could till now so it was a surprise when they were told that someone agreed to adopt them both.

They were happy to finally get a family so they were quite excited to see their parents. When they met them, they found that both their parents were quite good looking and looked rich. Akira didn't understand why they needed to adopt children but he didn't put much mind in it and simply followed them home.

While sitting in their car Akira was quite excited and asking a lot of questions while Silvia was quietly listening. While he was asking soon his eyes start to feel heavy and he fell asleep. When he woke up, he found himself in a wide bed in a luxurious room with Silvia sleeping beside her and an unknown girl with black hair staring at her face but.....she had cat ears and tail which made his brain stop working and he involuntarily uttered " cute " which made the girl blush.

( Back to the current flashback )

Kuroka looked at the face of everyone present in the room. Shirone was crying while hugging her because she could feel her pain, Silvia was a child who didn't know what's happening because she has not faced experimentation yet so she had a curious face but when her eyes landed on Akira, it became complicated he was a boy who was quite brave and cheerful when he arrived and even easily accepted her being a yokai because in his words " it doesn't matter as long as you let me touch your cute ears " but after repeated experiments he broke down but for a human, it's quite good that he didn't go insane till now.

She had just heard the researchers say that they were going to start 'that' experiment on him. She knew that no human had ever survived 'that' experiment and every subject had died indiscriminately. She didn't know how to break the news to the boy who called her ' Big Sis Kuroka ' she knew that his chances of survival was close to zero so she decided to keep the news to herself so as to not break his hope.

( CLIFFHANGER........YEAH CURSE ME ALL YOU WANT )