The Testament of Sister New Devil (Japanese: 新妹魔王の契約者(テスタメント) Hepburn: Shinmai Maō no Tesutamento?) is a Japanese light novel series by Tetsuto Uesu with illustrations by Nekosuke Ōkuma. Seven volumes have been published by Kadokawa Shoten since 2012 under their Kadokawa Sneaker Bunko imprint. A manga adaptation has been serialized in Kadokawa Shoten's Shōnen Ace magazine since May 2013. A second manga adaptation has been serialized in Hakusensha's Young Animal Arashi magazine since February 2014. An anime adaptation started airing in January 2015.