Both have a FL from the real modern world who enters a story, and ends up becoming involved with the plot's antagonist.
In a story, the ML is supposed to be a destructive villain who falls in love with a noble lady (the FL of the original story). But the true FL (a modern day woman) accidentally gets sucked into the story where she takes over the body of a woman (not the original FL) and starts to interfere with the plot to ensure the right outcome. The "villain" ML softens and seems to fall for the true FL after she seems to fall for him first (despite her obvious interest in the SML, which makes the ML quite jealous).