The events take place in a parallel reality. The Demon King named Sadao is just one step away from conquering the world. However, his opponent, Emilia, ultimately emerges victorious. Sadao is forced to relocate to another dimension: modern Tokyo. Since "world domination" is the only skill the Demon King possesses, he struggles to adapt to his new living conditions. Sadao is compelled to find a job in order to cover his expenses.