Quick Transmigration: Turning My Life Around, The Supporting Woman's Guide to Rising to the Top

[Quick Transmigration + 1v1 + Slaying Scumbags + No Fixed Couple + Happy Ending] Some supporting heroines have their once-happy lives ruined after being targeted by the heroines of their novels. After they die and enter the underworld, they learn that they were merely supporting characters meant to advance the plots of their fictional worlds. Their intense resentment throws the underworld into chaos. Shen Ning works for the underworld. At her superiors' request, she takes the place of these tragically murdered supporting heroines in their original worlds, trouncing the scumbag heroines, stealing their men, and building happy lives of her own. (The heroine in every mini-world is named Shen Ning.) World One: The frail younger sister who depends on her brother In the original story, the heroine is dating the original Shen Ning's brother, Shen Yan. She can't stand Shen Ning, a timid younger sister who freeloads at home, and constantly smears her behind Shen Yan's back without making it obvious. After learning that Shen Ning and Shen Yan aren't related by blood, and that Shen Yan cares deeply about her, she secretly contacts human traffickers and has Shen Ning kidnapped. From then on, Shen Ning's life becomes worse than death. When Shen Ning, an underworld employee, arrives: Shen Ning: "Hmm. That's it?" Shen Yan: "As expected, my little sister can't live without me (besotted expression)." Shen Ning: "..." The original heroine: "..." World Two: The supporting heroine refuses to be paired off World Three: The pitiful girl in a paranormal novel