Yamibo: Darkness, The Hat and the Travelers of the Books

Hazuki arrives in the Great Library and meets Lilith, who develops a crush on her because she contains the essence of Yami, once the protector of the Great Library and Lilith's lover. Hatsumi turns out to be an incarnation of Eve, who Lilith wants returned to the Library. Hazuki unenthusiastically accepts Lilith's help traveling the worlds. (Source: Wikipedia)