The Testament of Sister New Devil

Synopsis

Basara Toujou is a high school student whose father suddenly remarries and brings home two beautiful step-sisters, Mio and Maria. However, his father immediately leaves for "business," and Basara discovers his new sisters are actually a rookie Demon Lord and a succubus. After a master-servant contract goes hilariously wrong, Basara—who belongs to a clan of "Heroes"—becomes their master. He must now protect Mio from other demons and the Hero clan itself, often having to perform "intimate" rituals to strengthen their bond and her powers.