Shinmai Maou no Keiyakusha (新妹魔王の契約者 Shinmai Maō no Tesutamento, officially translated as The Testament of Sister New Devil) is a Japanese light novel written by Uesu Tetsuto and illustrated by Nekosuke Ōkuma. Since 2012, five volumes have been published by Kadokawa Shoten under their Kadokawa Sneaker Bunko imprint. The light novel was adapted into a manga series and has been serialized in Shōnen Ace magazine since May 2013. An anime adaptation has been announced.