The Book's Cannon Fodder Villainess: I'm the Best at Changing the Plot!

[A restrained assassin + a self-reliant heroine + a simple-minded older brother + a cheating male lead] [Breaking up the main couple + transmigrate into a book + System + staying true to one’s original purpose + conflicts in the outside world + putting things right + unexpected contrasts] There is a cold, aloof assassin who silently gives everything, yet is misunderstood because of special circumstances. In his eyes, the heroine is a light of salvation. A misunderstanding gradually drives them apart... There is the original male lead, whom the heroine keeps putting down. The two never got along, but the original male lead is a masochist. He falls for the heroine, who constantly needles him, with a love that is both restrained and intense. But things are far from that simple... (An ambitious schemer meets a devoted romantic.) There is a god-grandfather who treats her as his own and indulges her with boundless patience. There is also an all-around genius master: an eighteen-year-old heart, an appearance in his thirties, an actual age in his fifties, and seniority befitting someone nearly seventy. (Their relationship is purely that of master and disciple, formed out of mutual admiration. There is no melodramatic, tortured master-disciple romance.) What Wang Yan finds most unbelievable is that she meets a heroine from the latter half of the original book, whose traits are yandere, scheming, and haughty. This woman wants to tame her into a dog. (This happens much later. The leading lady doesn’t appear until around Chapter 150.) Wang Yan transmigrates into a book and gains a simple-minded older brother. Seeing him desperately protect her, she is deeply moved, having been hurt by family herself, and resolves to protect him. Armed with a sign-in System, her main job is to change the plot and break up the romances between green tea bitches and the main characters. She never expects to get dragged into the mess herself, turning what should have been a satisfying urban power fantasy into a tragic romance.