The Executioner and Her Way of Life, Vol. 4 (manga)

After putting a stop to Archbishop Orwell-s plans, Menou leaves Garm with Akari in tow, seeking a new way to kill the Otherworlder. In Libelle, the port city where one of the Four Major Human Errors is sealed, Menou and company are tasked with finding the origin of the -monstrine- drug circulating among the people. But as they look into their greatest suspect, Manon Libelle, Akari notices that their fates are gradually veering off course-