School for Devil Maidens

Nyx is a High Demon who finds herself trapped in a tiny, childlike body after three reckless noble girls summon her from an old grimoire. Forced to enroll at their academy and play along with their schemes, she would much rather just pass her classes. But ruins, secret passages and a hidden network of demons who hail her as their lord drag Nyx into a conspiracy that could set humans and demons against each other.