okay guys i don’t mean to fight too and this is not by any means a negative comment. they are not related, we know this. to me, the issue is more a matter of nomenclature than actual morals/incest. i’m simply questioning how their relationship will develop when they start dating:
will she keep on calling him brother? will she walk over it as if it’s nothing? when will she stop acting like this fictional world isn’t the world she lives in now? (honestly why all fl in transmigration stories are like this...) this kind of questioning
i mean she saw some random furry spirit dudes nothing else will be as surprising here hakwksksh
I think you might be forgetting something. This is a translation. Which means the real dialogue is in korean. In this language, Oppa (Old brother) and Noona (Old Sister - here, noonim) are used by almost everyone, be it couple, friends or real family (unless they find it cringy which is somehow normal). In this case, Ran uses the title of little brother to call him, since it shows a closer relationship. It might not be about the real fact that they are step-brother and step-sister. Since they never lived together, it would be pretty strange to call each other as brother or sister with the real intent of it, right?
I don't even understand how can people still think the translation for oppa or noona in korean webtoon would always means family. Since that's NOT the case. Just like the Daddy issue in english.

okay they aren’t siblings or related by blood, yustav doesnt see her as a sister: so why does she have to call him brother all the time it feels so awkwarddddd the issue lies exactly there, whY force this brother thing if they are meant to be the webtoon/novel couple?
when they start acknowledging their feelings for each other or when yustav asks her to see him as a man she will just suddenly get over the brother complex and poof forget she treated and called him as a younger sibling all this time? urghhhh author why did you do this......