Summary:

"Hey, you said you wanted a little sister, right?" First-year high school student, 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 will be getting remarried.

He then departed overseas after bringing Basara two beautiful step-sisters. But Mio and Maria's true identity are actually the newbie Demon Lord and a succubus!?

 

The battle between Demons and Heroes begins!!!