Story
At the mysterious orphanage where Sheena lives, death is nothing new to its residents—girls who no longer have families of their own, who are raised as weapons of war, taught to kill and take the lives of others without batting an eye. Everyone, that is, except Sheena, who wishes for nothing more than the growing conflict around her to end. On the night of her roommate's death, Sheena meets a strange girl covered in blood, who smiles despite the turmoil surrounding them. The next day, the girl appears as a new student in Sheena's class and introduces herself as Mimi.
Synopsis via AniList (English).