Luce To Shiro No Keiyaku

a brand new fantasy manga by mikanagi touya, the creator of “karneval”! after losing her foster parents, luce lives together with her younger sister, until suddenly one day, a woman named athesia appears before her with an unusual request: “would you be willing to become the lover of my fiancé?” she is then abruptly taken to meet rioverna, the young head of the gailenche family – one of the nation's five great families. what follows is the establishment of a strange contract between the two?!