It was announced by their official website that Shinmai Maou no Testament (Testament of Sister New Devil) will be receiving a 60-minute OVA. The official title of the OVA will be Shinmai Maou no Testament Departures. The OVA is slated to open in Japanese theaters on January 27 and will screen for about two weeks. The plot of the OVA has not been revealed as of yet.
The OVA will get a home media release on March 28. It will be available on both Blu-ray and DVD. In addition to the disc, it will also come bundled with a new novel by Tetsuo Uesu, the author the original light novel series. The light novel received two anime adaptions, the first of which aired in January of 2015 while the second season aired in October of 2015. FUNimation is set to release both seasons on home video through its partnership with Crunchyroll. The DVD/Blu-ray combo packs will be available on October 31. A limited edition will also be available, but you can only obtain it online.
MyAnimeList.net describes the story of Shinmai Maou no Testament as follows:
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…
