Brothers Lucifer, Mammon, Leviathan, Satan, Asmodeus, Beelzebub, and Belphegor are among the most powerful demons in the Devildom, serving as officers on the student council at the Royal Academy of Diavolo (RAD). However, being avatars of the seven deadly sins, their behaviors often tend toward the extreme. Their everyday antics belie their high status and fearsome reputations among others of their kind. When viewed behind the scenes, the members of this family are more lovable—and laughable—than they first seem!

A series of shorts parodying the main series Prism Ark.

The Sablum Empire has been attempting to take over the kingdom of Windland for many years, and are now plotting with the mercenaries Sister Hell and Darkness Knight to start a new offensive using powerful magical beings called Angels. Hyaweh, a carefree yet talented swordsman, and Priecia, who just might be the lost princess of Windland, are enrolled at the Knight's Academy in Windland to hone their skill at swords and sorcery. There they meet many friends and allies who can help them protect their homeland from the impending invasion.

The charming incarnations of the seven deadly sins—brothers Lucifer, Mammon, Leviathan, Satan, Asmodeus, Beelzebub, and Belphegor—can never seem to keep out of mischief. They are demons feared across the Devildom, but, at the Royal Academy of Diavolo, one human transfer student has captured their collective hearts. Whenever the brothers miss them, they engage in ridiculous antics to keep themselves entertained, and they even drag others into their neverending shenanigans.