
the Sei that is shown in this story hasn't been like that at all! We've been hearing his thoughts for nearly 100 chapters, and he wasn't having 'I hate you, Mom' and 'why did you make me be born' type thoughts when these events happened.
Is dream mommy gonna say told her to throw him off a cliff when he was a baby too? ( ̄へ ̄)

if Ida's story is true, then I think Glasses ho did it...
1) She's been manipulated into doing things before, and her life's strategy is to suck up to the powerful—With no cameras at the resort MC isn't so powerful anymore, so maybe Cooking Mama Shiori got her to do it while she stayed back and had an alibi
2) Haruka was incredibly strong...like she gives Bruce Banner a run for his money. In order to over power her, the person would need to surprise her with their attack. She people she might trust enough to let her guard down: MC, Shiori, and Glasses, because everyone believes her to be stupid. NO ONE trusts No Questions Girl, so she would have been on guard if alone with her.
3) Maybe Glasses wanted Revenge?

ALSO CAN WE TALK ABOUT THE FACT THAT SIGMUND IS BEING LET OFF EASY
they're just like "he did it all because he was jealous of lilith, silly man uwu"
DUDE HE WAS THE ONE WHO WAS RESPONSIBLE FOR LIKE 95% of the rape and incest and murder in this story
he bewitched Everybody???
Killed hundreds???
He raped his oWN SoN
like honestly i know they brought in Super Incel Beckenbauer to be the Big Bad, but for me it kind of... made it a bit weaker
Like I barely care about beckenbauer and his incel plot, but My Hate for Sigmund Knows NO BOUNDS???? HE WAS ALREADY THE WORST ALL ON HIS OWN
Like honestly I wish they just kept him as the top evil bitch because he was much wilder and more intimidating and I wanted to see him pay
cuuuuuuute~