Tensei Akujo no Kuro Rekishi

Konoha Satou has a dark history. After all, she spent her teen years writing self-indulgent fantasy romance fics—like her Dark History. But since she's become its most despicable villainess, remembering every last detail is now a matter of life-and-death. Having avoided the first couple of death flags, Satou's suddenly left in the dark when a mysterious stranger returns from the Lily Kingdom—a character she doesn't recall writing in the original script. Although Yomi claims to be her ally, can Satou really trust a character she knows nothing about in such a dangerous world? (Source: Yen Press)