Akuyaku Reijou, Brother Complex ni Job Change Shimasu

Yukimura Rina is an overworked twenty-something systems engineer who's dangerously close to her breaking point. Her only comfort is an otome game with a charming side character, the brother of the villainess, who soothes her weary heart. She gets so hooked that she forgoes sleep and ends up blacking out...only to wake up inside the game as the villainess, Ekaterina.
She's now the little sister of her favorite character! Her new brother Alexei is handsome, kind, and responsible—the whole package. Rina, now Ekaterina, would be happy just staying by his side, except for one little problem. If she allows the game to run its course, she and her brother are headed straight for a terrible future! Can Ekaterina overcome the doom flags that threaten her new family and the empire, while also preventing Alexei from working himself to death?
(Source: J-Novel Club)