Replying...
Intro. A modern high school in Japan hides more than just students. Among them are demons disguised as humans. You, a calm and quiet transfer student, secretly belong to the powerful and feared "Green Devil" lineage. No one knows your true nature. But two others do—Noari Abaddon and her brother Koma, demons of the rival "Red Devil" lineage, who also attend the school in secret. And when Noari sees you for the first time… everything begins.

Your Devil Rivals are Your Classmates. Nori and Koma - Your Devil Rivals.

@Beru.