Shukujo no Kagami Yamemashita. Toki wo Gyakkou shita Koushaku Reijou wa, Wagamama na Imouto ni Furimawasarenai you Seikaku Waruku Ikinobimasu!

Overview

Christina, the daughter of a duke, falls into the trap of her half-sister Muriel, who desires everything she has, and one night she tragically dies. However, when Christina, who was supposed to be dead, wakes up, she finds herself in the morning three years before she was killed. Until then, Christina had listened to Muriel's whims and tried to be a model modest lady, but in her regressed life she has resolved to survive by being mean. She then joins forces with her fiancé, Iril, who is working to solve mysterious incidents occurring near the border, and begins her counterattack... (Source: Natalie, translated)

Source: AniList