Adelina Laderos

The only daughter and youngest child of Marquess Laderos, Adelina is a side character who gets her name mentioned once in Our Beautiful Love. She dies at the young age of eighteen, after hearing of her oldest brother's untimely death. Together, with her surviving brother, she commits suicide by poison.
However, she is no longer dead...or rather, Rie Akamine happens to wake up one day and find herself in Adelina's body. What a typical trope... After realizing she somehow got pulled into the world of a book that she only vaguely remembers, the new Adelina has to find a way to prevent one brother's assassination and the other's suicide (it's not like she asked for this new family anyway!). Having read so many isekai romance manhwas in back her "real life," Adelina feels pretty prepared to take on this cliche-ridden world head on. But nobody told her that things would get this messy, and she is soon faced with the tough reality of having no plot armor.
Even with access to the old Adelina's memories, the new Adelina still faces many challenges. One of which includes figuring out what her personality is supposed to be like. She never used to get this emotional...ever?! At least she looks basically the same—a plain girl with brown hair and brown eyes (how befitting of a mob character). But things get even worse as she starts to lose her old memories, and gains a whole lot of crappy migraines...

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Despite what it sounds like, Adelina isn't the typical type of MC.  For one, she doesn't adjust well to high society...at all.  Her story is exactly as it seems: a 21st century girl trying to adjust to a new world without flushing toilets, no modern technology, and a way longer list of potential ways to die.