"The Contract of the New Sister Devil Season 2" tells the story of "You said you wanted a sister, right?" The father who announced his remarriage to high school student Tojo Basara brought two girls who became his step-sisters home to live with him, but he went on a business trip abroad. After their father left, the two girls, Mio and Maria, changed their attitudes 180 degrees and planned to conquer Basara. Unexpectedly, their true identities are the new demon king and the dream demon. However, when they signed the master-servant contract with Basara, the hammer turned out to be a reverse contract, and Basara became the master instead.