Long ago, there was a monk named Myoue who could bring anything he drew to life. He quietly lived with his wife Koto—a black rabbit in human form—and their three children: Yakushimaru, Kurama, and Yase. One day, the high priest of the land concluded that Myoue's drawings caused too many problems for the locals and ordered him to find a solution. In response, the family secretly fled to an alternate world of Myoue's own creation—the Looking Glass City. Everything was peaceful until Myoue and Koto suddenly vanished. Their three children are left to take care of the city, and Yakushimaru inherits Myoue's name and duties. Stranded in this alternate world, their problems only get worse when a young girl—also named Koto—crashes down from the sky and declares that she is also looking for the older Myoue and Koto. Armed with a giant hammer and two rowdy familiars, Koto just might be the key to releasing everyone from the eternal paper city.

On the run for crimes she did not commit, disgraced noblewoman Charlotte Evans collapses deep in the forest. A sorcerer named Allen Crawford—also known as the "Demon Lord"—finds and defends Charlotte from her pursuers. Since she has no place left to go, Allen takes pity on Charlotte and offers to hire her as a live-in maid. Allen quickly realizes that Charlotte has faced ridicule and hatred all her life from her so-called noble family, and she has never known what true freedom feels like. He decides to teach her about all the naughty things the world has to offer and enables her to surrender to her whims and impulses. Charlotte's sweet innocence proves an obstacle to his plans, but Allen is determined to show her the kind of life her family has denied her. Although he despises being social, Allen begins to open himself up to Charlotte. The longer they live together, the more they discover their similarities. Though most people have abandoned them, the duo promises to stay together, oblivious to their budding feelings for each other.

Losing their war against Heaven's angel army, the demons of Hell are on the cusp of collapse. As a last ditch attempt to turn the tides of the war, the demons send Akutsu Masatora to the mortal plane on Earth to save their homeland from the angels. Disguising himself as a high school student, Akutsu seeks to recruit someone with the capability to lead the demons to victory. Akutsu does not have to look far: among his classmates is the magnificent Lily Amane, a transfer student who seems like the perfect candidate for Akutsu's plans. But as luck would have it, Lily is one of the very angels that Akutsu is meant to be fighting against, and his attempt to recruit her might end up being the biggest blunder in the failing war. Worse yet, Akutsu may fall in love with his own worst enemy.