The midoriya demon siblings

Chapter 1: "I despise this world..."

Izuku and Ume Midoriya, they were both four years old when it happened...

They learned the true nature of this world... In this world they only have eachother, they can only count on themselves,

"I promise we'll always be together" said Izuku hugging his younger sister in his arms, they were in the street, they had escaped Inko, their 'mother' some days ago, they managed to escape her abuse, but now they were outside in the cold, Izuku was always despised, he was ugly and his quirk didn't help his case, since he got his quirk he was extremely skinny, so much so that it looked like he had no organs in his stomach area, you could clearly see his ribcage, no matter how much he ate he always looked like this, but he was extremely strong he was able to break iron with his sheer strenght like it was a piece of paper.

"please help me and my sister!" he plead on the street to the persons and the heroes walking around...

but nobody came...It's a lesson we all have to learn one day, you can only count on yourself in this world where power is everything.

Ume, Izuku's little sister, always clung to him, she had such a beautifull face that you couldn't believe that they were siblings, she had beautifull green hair and eyes, she was the exact opposite of her brother and yet they never once separated.

After two years of stealing and living on the street, a man in a suit approached them,

"Hello children" he said in a fatherly voice, however Izuku was cautious and on guard,

"I would like to help you, i have seen that you were struggling recently"

"..." he stood in front of his sister in a defensive fashion while she clung to him,

"Oni-chan who is this?"

"hello child you may call me All for One, would you like to accompany me to eat ?"

"!!!"

"C-can we oni-chan?"

Izuku hesitated, a guy appeared of nowhere and proposed food to them? However Ume hadn't eated in a while so...

"...fine, try something funny and you're dead"

" Don't worry child, I do not wish to harm you"

10 minute later they were inside of a bar, Izuku was nervous and was violently scracthing different part of his body until it bled, however his regenaration abilities took care of it, something that All for One noticed,

"Tell me boy, what is your quirk?"

"And why should I tell you!?"

"Please child I only wish to talk, if you do not wish to tell, then I don't mind. Now will you tell me what you two were doing on the streets ?"

Izuku was staring at the man that extended to him and Ume food, Ume scarffed the food down like she didn't eat in weeks...wich was the case.

Izuku sighed and told him their story,

"My sister was named after the disease that nearly killed our 'mother', we were born in the lowest class of Musutafu, My mother didn't want me and nearly killed me several time before i was even born, and she still tried to kill me numerous time after i was born, and yet i survived, I was mocked for my ugly voice and appearance and rocks were thrown at me for being filthy, when I got hungry I ate mices and insects. After Ume was born things didn't really change for me, but she was praised for being beautifull, I wasn't jealous, I was even happy that my sister was so beautifull, having someone as beautifull as her as a sibling really helped me with my inferiority complex, but once our quirk manifested, we were seen as monsters, as beings that shouldn't be allowed to exist, one day after our mother tried to kill Ume, I created a scythe made of my blood, my flesh and my bones and split her face in half, killing her on the spot...it's been 2 years since we were on the streets, we left the house as fast as possible and fled, I stole food for Ume and  I ate what I could"

All for One was listening very carefully

"I despised this world!" he screamed scratching himself even more "This society kept taking things from me after never giving me a damn thing!  Unforgivable! Unforgivable! I want to destroy this society and show them that they are nothing but egotistical and pathetic creatures that aren't even worth a damn rock!"

All for One smiled, "The join me", Izuku was surprised and looked at him in confusion,

"Join me and help me destroy this corrupt society to create a new one, You wish for something? then take it! You wish to destroy something? then destroy it! Tomura!"

then a boy with white hair and scars around his neck came 

"I present to you Tomura Shigaraki, the one that will help me destroy this society and will be the one to pass down my legacy, help him grow and get strong you and your sister, and show the world that you are here!" the sibling thought about it for a while and talked

"Oni-chan? should we join them? He's right after all...we need to show the world that we exist too!"

Isuku said nothing but smiled maniacally

"alright then, let's show the world that WE are here"