Luisha, a boy, is unexpectedly trapped in an alternate dimension created by a hero. There, he encounters the Demon Lord and Dragon King, who were supposed to have been defeated by the hero three hundred years ago! Becoming friends with them, Luisha is trained by the pair, transforming from a weak boy into a legendary warrior, a "Demon Dragon Knight," possessing the combined powers of demons and dragons. Using this power, he escapes the alternate dimension and enrolls in a magic academy to help the still-sealed Demon Lord and Dragon King. Having been trained extensively by them, Luisha causes a ruckus at the magic academy!