Welcome to the world or Rising of the Shield Hero, where the Kingdom of Melromarc had summoned 4 Cardinal Heroes to defend the Kingdom from the Waves of Calamity like:

The Sword Hero Ren Amaki

The Bow Hero Itsuki Kawasumi

The Spear Hero Motoyasu Kitamura

And the Shield Hero Naofumi Iwatani

However an unexpected development had occurred which leads to the summoning of a Fifth Hero unknown to Melromarc and the entire world.