Responses
to be more accurate the first wife was being tortured and bullied by the second wife (protag's mother), who was trying to kill the blonde daughter. so to protect the blonde daughter she made a deal with a demon to protect her child, and then the first wife died.
what the first wife didnt know is that the demon just killed her child and possessed her body.
Spoiler:
so turns out that the blonde daughter was NOT FAKE and is actually being controlled by a demon she was in a state of DEAD (REAL DAUGHTER) /ALIVE (DEMON) because the father didn't care about the first wife therefore the 1st wife got her revenge and made a deal with a demon who wants to end the world then after the Blonde that is being controlled by a demon successfully BRAINWASH THE FATHER then executed her only LIVING DAUGHTER then the end of the world happen the father made a deal with a demon who doesn't want to end the world and reverse time then that's how her only living daughter got reincarnated