I was born in the surface and kidnapped to becoma a Little Sister, as well as my elder sister Akame, who already reached the age of a Big Sister. We didn't meet a lot... Until she attacked me. I killed her and revived her with the Dead Ringer Vigor, turning her my lovely obedient puppet. A year later we found the Lot 111 and I used it to become a Big Sister instantly. Good luck myself!
In a place where the only law is the law of evolution, nature can come to its finest, glorious and beautiful.