Twenty-year-old otaku Naofumi Iwatani is mysteriously transported to the otherworldly kingdom of Melromarc. Appearing before the King, Naofumi and three other summoned individuals learn that they are each one of the Four Cardinal Heroes who are tasked with defeating the malicious "Waves of Catastrophe." However, Naofumi is given only a measly shield and dubbed the "Shield Hero," the weakest of the Four Cardinal Heroes. Owing to his lack of power, none of the kingdom's mercenaries wish to aid h