Ep 1. The Day I Got a Little Sister

The Testament of Sister New Devil follows the story of Basara, a high school student whose father remarries and brings two step-sisters into the family, Mio and Maria. In the first episode, entitled "The Day I Got a Little Sister," Basara begins to adjust to his new family life when he discovers that his step-sisters are actually demons.

At first, Basara is skeptical of Mio when she tries to convince him of her true identity. However, when his father and step-mother depart on a trip, Basara is left alone with Mio and Maria and begins to understand just how powerful they really are. It turns out that Mio is the Demon Lord's daughter and is being hunted by other demons who wish to eliminate the threat that she poses.

As Basara starts to grasp the complex situation that he has found himself in, he also learns that he has inherited an extraordinary ability. He is now a member of the Hero Clan, a group of individuals with incredible powers who are sworn to protect humanity from the threat of demon-kind. With new responsibilities and powers at his disposal, Basara must decide whether to embrace his new role as a hero or hide away with his step-sisters, who are in grave danger.

As the episode progresses, Basara begins to develop a bond with Mio and Maria, recognizing that no matter where they came from, they are now a part of his family. However, that family dynamic is quickly put to the test when a group of demons arrives at their doorstep seeking to capture Mio. In a heart-pounding battle that showcases the full extent of Basara's abilities, he and Mio fend off their attackers and emerge victorious.

The debut episode of The Testament of Sister New Devil is a whirlwind of emotion and action, setting the stage for a story that will explore themes of family, power, and loyalty. With stunning animation, a gripping story, and compelling characters, it is an anime that will leave viewers on the edge of their seats, eager to see what will happen next.