It centers on Basara Toujou , a seemingly normal boy who encounters his new family members Mio and Maria under the pretense of his father's "rearranged marriage" with their mother. In reality, however, the "sisters" are actually demons who escaped from the Demon Realm after Wilbert 's passing. In order to protect his "stepsisters" who he cherishes, Basara must do whatever it takes to protect them from harm, and the people after Mio's powers. The first season of the series that primarily focuses onto the first three Light Novel Volumes and three major story arcs: First part is about an introduction of the Naruse Sisters into Basara Household as the "new family members" in order to seek asylum after Wilbert's demise.