When an interdimensional gate opened in the mountains of Eterna, demons poured through and the six human kingdoms set aside generations of conflict to fight a common enemy. Five years of bloodshed ended with the Peace Treaty of Hope, negotiated by three heroes — two humans and a demon.

The treaty raised a tower over the gate and bound its guardian to absolute neutrality. He has interfered in human politics three times. Those who have met him describe him either as a kind, charismatic young man or as a devilishly cunning monster, which earned him the title Devil of the Tower.

The saga follows his son, a seventeen-year-old who enrols at the most prestigious academy on the continent as a commoner of unknown origin, carrying a curse laid by the Demon King himself.