"Hey, you said you wanted a little sister, right?" Highschool freshman, Toujo Basara, was suddenly asked by his father and fell into a state of panic. On top of that, the eccentric father told him he would be getting remarried. He then departed overseas after bringing Basara two beautiful step-sisters. Things aren't as they seem in this series, as Basara discovers that his new "family" has a few secrets he's yet to unveil. Adaptation of the [Light Novel](https://www.novelupdates.com/series/shinmai-maou-no-keiyakusha/) series written by Uesu Tetsuto and with illustrations by Ookuma Nekosuke.