Erie Daemon is a high school English teacher who enjoys his quiet life. One day, his class gets attacked by a demon. After saving his class from the demon, his world seems no longer peaceful. Demons keep coming to corrupt the middle realm, and the Defense Against Hell’s Supernatural Activity Division threatens Daemon's teaching license and his peaceful life if he doesn't use his skill to find out what type of demon Demelza is. However, does she seem to be just a normal girl?