Sumigomori no Sumijo Maou wa Saikyou Juusha ni Koikogaremasu

The story revolves around the human student Sumi, who attends a magic school in the human realm. One day, a servant of the demon realm appears before him and informs him he has been appointed as a new servant of the demon queen. A romantic comedy between the demon queen and her servant ensues as a heart of charcoal catches fire from the flame of love.

(Source: Anime News Network)