The first manga adaptation of 'The Testament of Sister New Devil' began serialization.
The anime was officially licensed for English release by a North American distributor.
Jin Mazama transfers Tatsumi into his house after Tatsumi's father is forced to go overseas, beginning the story.
Upon arriving at Jin's house, Tatsumi meets his two new step-sisters, Mio and Maria, who turn out to be demons.
Mio and Maria reveal to Tatsumi that they are demons and that Tatsumi has been contracted as their master to protect them.
To protect Mio from hostile forces, Tatsumi signs a master-servant contract making him her master.
Akatsuki, a powerful ninja and ally, comes to aid Tatsumi and Mio against threats from the demon world.
Tatsumi, Mio, Maria and Akatsuki face off against demons trying to kidnap Mio for her demonic powers.
Tatsumi undergoes intense training to better protect Mio and Maria from increasingly dangerous enemies.
Sera, a Demon Lord candidate and part of the opposition, begins to create trouble for Tatsumi and his household.
Tatsumi and the girls confront Sera in a decisive battle to protect their home and maintain peace.
After multiple battles, Tatsumi's relationship deepens with his demon sisters as they rely on each other more.
It is unveiled that Tatsumi himself carries demonic powers inherited from his family line.
Tatsumi, Mio, Maria, and allies face the Demon Lords to resolve ongoing conflicts threatening their world.
After the defeat of the Demon Lords, the world returns to a fragile peace and Tatsumi’s family stabilizes.
