Still have no idea what is going on
A couple corporate slaves reincarnated into an otome game. The woman played (and loved) the game in her past life and, like all heroines in a villainess manga, is aiming for the reverse harem since she regained her memories early in life.
The man has (seemingly) never heard of the game and didn't gain his memories until
significantly later, so his original otome game personality is, currently, still in almost complete control.
The villainess in the setting is also truly a horrible person and not
just a woman lashing out at her fiance (and all his friends) ignoring her and denigrating her in favor of some random girl who just showed up and stole the scene.
TL;DR: Two reincarnators, one knows the setting, one doesn't, and there (apparently) isn't a single decent person among the cast.