The Battlefield SaintNewSenjou no Seijo - Imouto no Kawari ni Koushaku Kishi ni Totsugu Koto ni narimashita ga, Ima wa Shiawase desu

Fina, who is plain compared to her sister referred to as the Holy Maiden, faces harsh treatment in her family's earl household. While working as a military doctor on a perilous battlefield, she encounters Leon, a duke's knight. After saving him from near-death with healing magic, she is later proposed for marriage! Despite doubting if he's mistaken her for her sister, Fina finds herself leading a blissful life in the duke's household, contrasting starkly with her own family's mistreatment!