So, here's a bit a lore/story drop/explain for this "au" of the Sumino siblings:

In this Au, The others members of the sdu are truly "normal" people with their past and family being true. They were chosen due to their compatibility with cryptoglobine (Like Sirei said,  but this time it's true)

Except for Takumi and Osaka:
Those two are artificial live being. A mix of futurum and Dr. Sumino DNA,  combined with some residue of the world death of earth.

The 2 were created and raised in the Kamukura hospital. Dr. Sumino work there and was one of the lead directors and "caretaker" of the 2 siblings. 
The 2 were called subject W.E 1(Osaka) and W.E 2(Takumi) before being named by Dr. Sumino. 
Their childhood was mostly composed of doing different experimentation and test to see the extent of their capacity. They were not always treated properly... close to being considered simple objects by some scientists. But Dr. Sumino always defended them and fought with the rest of the people on the project to consider the 2 children as human beings. 
She quickly became a mother figured for the subjects,  even though it wasn't her plan, but she couldn't help her self but too grown very attached to them.

Osaka and Takume have an original/hybrid form that they used to control but lost the capacity to "go back to" after their brainwash before being sent to the Academy. (Osaka is in her form on the drawing. I'll probably draw a more details form of the two another time)

For 8 years Osaka and Takumi lived together in the hospital. But one day, the building had a security breach and Osaka took the occasion to escape. She wanted to goes with Takumi, but she hadn't had the time/opportunity to "saved" him too. Something that she will always resent and hate herself for.
But outside of the Hospital, Osaka will lived an horrible life: She was in the poor and highly dangerous part of the artificial satellite. There she will be horrible treated by viscous adults (WARNING!!!!!!!!!!¡!!!!!!!!!!: MENTION/SUGGESTED HARD ,TRAUMATIC AND SENSITIVE SUBJECTS!)
She was abused, harassed, beaten and 🍇 for years. It's due to all this that she will develop 2 others personality (Tokyo and Hiroshima)

After 6 years, She will finally be found by a research team of the hospital and will be retrieved there and be send in the academy 2 years later.


Takumi was very affected by the "lost" of his sister and became less and less mentally present,  he started to follow orders of the scientist mechanically. 
In the meantime, Dr. Sumino was also deeply affected by the dissappear of her "daughter"
She became overprotective of Takumi and started to fought more and more with thr others higher ups of the project. Wanting to take Takumi out of it and taking him under her guard. 
Sadly she never achieved it and the "hundred line " project started without even warning her.


Ok, I think it's already a lot for now 😅
I explain more a next time if you are interested 👀

Dr. Sumino (Takumi and Osaka's[my oc] "mother") -oc content and "lore"