Also known as: 新妹魔王の契約者, 新妹魔王的契約者, 新妹魔王的契约者, The_Testament_of_Sister_New_Devil
The Testament of Sister New Devil (新妹魔王の契約者『テスタメント』), also known as Shinmai Maou no Keiyakusha, is a softcore erotic Light Novel written by Uesu Tetsuto and illustrated by Ookuma Nekosuke (Nitro+), published from September 2012 to August 2021.
It has two manga adaptations and an anime adaptation.