The Testament of Sister New Devil

High school student Toujo Basara expects an ordinary life until his eccentric father abruptly announces his remarriage. This sudden decision introduces Basara to two captivating new step-sisters, Mio and Maria. However, his domestic routine shatters when he uncovers their extraordinary true identities: one is a succubus, while the other is a newly crowned demon lord. The revelation plunges Basara into a dangerous supernatural world where chaos quickly ensues. An attempt to bind Basara into a magical contract as their eternal servant goes awry, resulting in a reversed pact that unexpectedly makes him their master. Thrust into this unprecedented role, he must navigate a perilous existence balancing two conflicting challenges. On one hand, he constantly struggles to resist his step-sisters' relentless seductive advances. On the other, he faces escalating threats from rival demon contractors determined to eliminate them. To survive this treacherous new reality, Basara must rapidly adapt, mastering the complexities of his sudden authority while defending his unconventional family from formidable enemies lurking in the shadows.