On a rainy day, an infant with a terrible destiny is left on a doorstep and abandoned.
Years later, that infant-- a young man named Akuto Sai --has been accepted as a transfer student to the Constant Magic Academy. On his way to the school he meets Junko Hattori, the scion of a clan dedicated to preserving the peace of the nation, and after he explains to her his goal of becoming an influential and noble man, the two become fast friends.
...Until Akuto goes through his medical exam, which includes free career counseling via magical smoking crow. The crow, who has never been wrong, pronounces that Akuto's future career is as the maou-- the demon king.
His friendship with Junko is immediately crushed as rumors of the return of the demon king, who nearly crushed society hundreds of years before, circulate throughout the school. Akuto's attempts to repair the relationship just result in more terrible rumors, humiliating Junko so badly that she swears she'll destroy him. Cue the entrance of not one, not two, but THREE other girls, all of whom have an agenda with Akuto...