Now You See Me, Soon You Won't

Spat out from the bowels of humanity comes a mysterious assassin bred from hardship and cruelty. Tossed into the Kuroshitsuji universe to fend for herself, she's apprenticed to an ambiguous undertaker and yet manages to captivate our infamous demon butler. What is she to do as she attempts to find her way back home? /UTxOCxSebastian; slowburn, Sebby appears: ch