Su Qian transmigrates into a Mary Sue novel as a foolish supporting female character who barely appears before being written out. After transmigrating into the book, she bears the heavy responsibility of changing the fate of the second male lead, the villain.
As she spends time with him, she discovers that although he shows signs of obsessive tendencies, he isn't actually a bad person by nature. If she can steer clear of the events that would turn him evil, she still has a good chance of completing her mission.
Su Qian tries to set the villain up with other people while also protecting him from events that might make him turn evil.
In the process, however, the villain gradually finds himself drawn to Su Qian.