Fukushuuki Laura: Oneesama wo Ikenie ni Shita Kono Kuni wa Mou Iranai

The Kingdom of Marquide has been locked in conflict with magical beasts. Two sisters, Laura and Layla, lived there in harmony. Until one day when the older sister Layla was chosen as the "saint," an important position in the kingdom. Court intrigue caused fissures in their relationship. Villainous aristocrats tore the sisters apart. Now Laura will set out to get her beloved sister back, in this epic tale of revenge!

(Source: Akita Shoten, translated)