Akuyaku Reijou, Brother Complex ni Job Change Shimasu

After being forced to work overtime for the umpteenth time in a month, Yukimura Rina drags herself home, exhausted and in need of some relaxation. She downloads an otome game, starts playing, and passes out...only to wake up as Ekaterina, the villainess of the game! Her new reality overwhelms her, but she soon recovers thanks to the care of her handsome, kind, and responsible new big brother, Alexei. There's one little issue, though. If the game follows its original scenario, only the worst awaits her and her dearest brother! Rina, or rather, Ekaterina, now has two goals: find a way to avoid doom, and protect her new big brother from the horrors of overwork!

(Source: J-Novel Club)