Airi Katagiri is just an ordinary high school girl until a mysterious magic circle suddenly transports her to another world. There, she finds herself in the Demon Realm, where a group of demons had been attempting to resurrect their fallen Demon King. Instead, their ritual summons Airi, and somehow, she has inherited the Demon King's power. Now an ordinary Japanese schoolgirl has been thrust into the role of ruler of the demons. With tensions between humans and demons already running high, Airi must figure out what it really means to become the new Demon King.