I'm trying to remember what manga this was. The main character was a girl who gets reincarnated into a story where her older brother is the main villain, maybe he was the orchestrator of a death game? I don't exactly remember. Since the brother initially became a villain because he was bored or sm, MC decides to make sure he doesn't get bored and tries to surprise him. He turns yandere...they were in a normal high school setting I think.

Death Game Manga no Kuromaku Satsujinki no Imouto ni Tensei shite Shippaishita.

fuck

yeah thanks!