Shinmai Maou no Testament

Toujo Basara, a high school student, faces an unexpected family change when his eccentric father remarries. His new step-sisters, Mio and Maria, are anything but ordinary. One is a succubus, the other a newly crowned demon lord. Basara is nearly compelled into a contract that would make him their eternal servant, but the agreement backfires, resulting in a reverse contract that places him in the role of master. As he navigates the challenges of his new reality, Basara must deal with the sisters' flirtatious behavior and the threats posed by rival demon contractors. His ability to adapt and survive depends on quickly understanding the complex dynamics of his new position.