Kon'yakusha wa Gimai no Hou ga Taisetsu Nanode, Futari ga Kekkon Dekiru Youni Shiteageyou to Omoimaru summary: Adela, a marquis's daughter, who has endured her fiancé Leonard's neglectful behavior for years. He always prioritizes his stepsister, taking her on dates, and constantly choosing her over Adela. Despite her attempts to bear with the situation, she finally reaches her limit when she catches Leonard kissing his stepsister and discovers that the pair are plotting to take over the marquisate. Heartbroken but resolute, Adela decides to fight back. She enlists the help of Leonard's cold, calculating older brother, Terence, and sets a meticulous plan in motion—not just to break off the engagement, but to ensure that Leonard and his stepsister can be together, while making them lose everything else in the process. (Art Lapsa) Kodansha-Comic Pixiv-Comic