Gunbured Sisters vol. 1 (Yuri manga)

In a decaying gothic city, warrior nun Dorothy is tasked with hunting down and slaughtering supernatural creatures. A member of the elite Crimson Sisters, she seeks to rid the city of the vampire population that plagues it. One fateful night, she encounters a wounded woman, Maria, only to discover that she has fangs and a strange parentage. Dorothy offers the half-vampire her best and only chance at survival: become my pet. Together, Dorothy and Maria will dive into the secrets at the heart of the vampire scourge that threatens to overwhelm their home.