Althea wished she could transmigrate into a different world. Even a book would do. And one day she did. But there was a teensy tiny problem.

The character she transmigrated into was the cannon fodder fiance of the male lead. The misunderstood girl that ends up sacrificing herself in the final battle after spending her last days in jail, accused of murder.

So she does the thing her books taught her. Tear the engagement and let the lovebirds deal with each other. That is about when things began to change.