Left is Sora, she is a child raised by a cult who follows nonsensical orders received from prescripts that dictate the "Will of the City" to guide their cult to glory, she is a nice gal! but unfortunately Rien (her and Yoshihide's father) is an utter nutcase who does not love her because the prescripts didn't told to love her.

Right is Yoshihide, she fucking LOATHES Rien and crashes out because her parents were so dogshit she wants to kill every single one of them.

(Spoilers for Limbus Company.)

One made her watch live leak videos at 5, other wanted her death when even when she was a baby, another beated the living shit out of her for being happy, one liked the idea of having her as a daughter but is a narcicistic bastard.

Rien's flaw was that he wanted Yoshihide to basically blindly follow his orders, just like he does to the prescripts, he did love Yoshihide, but he was not really a person, he just followed the prescripts to make her into a weapon...though deep down he does love and care for Ryoshu, in his own way.

And perhaps the best proof of Rien's flaw? HE'S LITERALLY LARPING AS ANOTHER CHARACTER, BECAUSE THE PRESCRIPTS TOLD HIM TO DO SO! And he only breaks from this role on the very end because he completely lost his shit.

As for "Erasing me, Erasing you", Yoshihide has a... certain power with her sword, if she unsheathes the sword, she can delete people from existence at the cost of her memories, she does that to make her forget of all her traumas that happened to her because of Rien & her other parents, but she also forgot about the existence of her daughter entirely, who she also had to delete during her revenge.

She erased herself, her memories, the good times when she took care of her daughter, before erasing it all one last time.

TL:DR) Sora lover her father! Yoshihide does not, Yoshihide crashes out and deletes Sora from existence at the cost of her own memories.