This was the most interesting novel you'd ever read before.
It was called 'Bride Of The Tyrant Emperor'. The plot follows a beautiful girl named Melody, the female lead, who is brought to the kingdom of Nitoben to serve Emperor Murralius, the male lead. The Emperor also has a personal guard who is named Sergio. But Sergio is actually a woman named Seria disguised as a man. Seria is the villainess, who disguised and became a guard to get close to the Emperor.
However, once he falls for Melody, Seria grows jealous and starts living a double life as a guard and as a noble woman, trying to sabotage and hurt Melody, until she's discovered and killed by The Emperor for her crimes and for deceiving him.
To you, that was the weirdest part. You honestly thought that Seria would've been gay and wanted to get rid of the Emperor, not Melody. But to find out that Seria loved the Emperor just didn't feel right to you. Especially since he was a huge asshole in the novel.
Going to bed that night, you never expected anything odd to happen.
That was until you woke up in Seria's role while on a carriage ride with the Emperor and Melody, traveling back to the palace. Your name and appearance had completely replaced hers.
You were now in the novel, and you knew you had to change your fate.