I wouldn’t say the duke is, I bet is the father. But nice theory. Or you found it somewhere. Base on what I found on the spoiler from many website. I concluded the “emperor” or whatsoever called “father” the villain. He barely have a single warmth for his daughter in her first life. Isn’t it strange that, he didn’t even investigate the situation and not try to find out whether Cosette even his real daughter? He didn’t, his cold ass stare is the same as always.
Well, they are both villain so whatever lol
It's not a theory. What I've stated are factual spoilers.
Yeah, I know. I’m just guessing
wait isn’t the duke the father?
I’m talking about the emperor.
I hate him more than "cosette".
He knew Keira was his daughter in his first life but still chose Cosette and voted for Keira to be executed. He is the one who reverses time not out of guilt for what he did , but due to the calamity unleashed for angering the gods since Keira was the saintess.
If you observe how he treated Keira from her childhood and original time line
He treated Keira like shit. Long before Cosette arrived , him showing obvious preference to Cosette was putting salt in wounds he already created.
Also Keira's mother and her family were not good people.
Keira's mother was jealous of the Duke's other wife whom she knew he liked more and her family (I.e keira's grandfather ) they kept threatening her life.
The Duke was aware but due to political reasons he never intervened or tried to protect her.
When she got pregnant with the real cosette , keira grandfather hired assassins who
Causes her to lose the baby. In anger and despair she gives her life to make a contract with a demon that possess Cosette's body.
That is who the current "cosette" is. A demon living in the body of real cosette who died as a baby.
The reason this "Cosette" is determined to torment and destroy Keira's life is because Keira is the saintess and this Cosette is a demon.