Basically, the MC was reincarnated on the body of the novel's villainess, and she was married to the Emperor or something. In the original novel, this villainess was cast aside (or was killed, i don't remember) after the heroine showed up, because there was a profecy that the emperor must marry the heroine or else the Empire would fall in ruin. When the MC reincarneted, the ML fell in love with her, and, when the heroine showed up, he refused to divorce the MC. MC thought they would be happy forever, but tragedies and disasters start to befall the Empire and people revolt. ML dies protecting the MC and buying time for her to escape. MC and the heroine are captured, MC drinks poison and dies. She wakes up and realizes she was brought back in time. She vows not to defy fate again and step down when the heroine shows up. That's what I remember.
Basically, the MC was reincarnated on the body of the novel's villainess, and she was married to the Emperor or something. In the original novel, this villainess was cast aside (or was killed, i don't remember) after the heroine showed up, because there was a profecy that the emperor must marry the heroine or else the Empire would fall in ruin. When the MC reincarneted, the ML fell in love with her, and, when the heroine showed up, he refused to divorce the MC. MC thought they would be happy forever, but tragedies and disasters start to befall the Empire and people revolt. ML dies protecting the MC and buying time for her to escape. MC and the heroine are captured, MC drinks poison and dies. She wakes up and realizes she was brought back in time. She vows not to defy fate again and step down when the heroine shows up. That's what I remember.