Shinmai Maou no Testament
English title: The Testament of Sister New Devil
Japanese title: 新妹魔王の契約者〈テスタメント〉
Alternative titles: Shinmai Maou no Keiyakusha
Type: TV
Source: Light novel
Episodes: 12
Status: Finished Airing
Aired: Jan 8, 2015 to Mar 26, 2015
Broadcast: Thursdays at 02:00 (JST)
Duration: 23 min per ep
Rating: R+ - Mild Nudity
Studios: Production IMS
Producers: Kadokawa Shoten, AT-X, Nippon Columbia, Kadokawa Pictures Japan, KlockWorx, Mobcast
Licensors: Funimation, Crunchyroll
Genres: Action, Supernatural, Ecchi
Themes: Harem

Running into your new stepsister in the bathroom is not the best way to make a good first impression, which Basara Toujou learns the hard way. When his father suddenly brings home two beautiful girls and introduces them as his new siblings, he has no choice but to accept into his family the Naruse sisters: busty redhead Mio and petite silver-haired Maria.

But when these seemingly normal girls reveal themselves as demons—Mio the former Demon Lord's only daughter and Maria her trusted succubus servant—Basara is forced to reveal himself as a former member of a clan of "Heroes," sworn enemies of the demons. However, having begun to care for his new sisters, Basara instead decides to protect them with his powers and forms a master-servant contract with Mio to keep watch over her.

With the Heroes observing his every move and the constant threat of hostile demons, Basara has to do the impossible to protect his new family members. Moreover, the protector himself is hiding his own dark secret that still haunts him to this day...

[Written by MAL Rewrite]

Shinmai Maou no Testament adapts the first 3 volumes of Tetsuto Uesu's light novel series of the same title.