Shinmai Maou no Testament

Toujo Basara, a high school student, faces an unexpected turn when his eccentric father remarries, introducing him to two unusual step-sisters, Mio and Maria. Upon learning that one is a succubus and the other a newly crowned demon lord, Basara's life becomes complicated. He is nearly compelled into a contract with them, positioning him as their eternal servant. However, the contract backfires, resulting in Basara becoming their master instead. Navigating the challenges of resisting their seductive behaviors and dealing with threats from rival demon contractors, Basara must quickly adapt to survive in this new, dangerous situation.