Shimai Gyakuten Game: Zutto Kiratteita Utsukushi Sugiru Ane

Sumire is a popular model who's newly engaged. She has a sister named Nobara. At the engagement party, Nobara discovers a shocking fact: Sumire, has been deliberately stealing the men Nobara's fallen in love with, calling it a fun "game". Furthermore, the man Sumire chose to marry was Hikaru, someone Nobara's always admired and stood by at work... Having learned the truth, Nobara joins the "game", seeking revenge by any means necessary...! (Source: MangaPlaza)