Iwatani Naofumi was summoned into a parallel world along with 3 other people to become the world's Heroes. Each of the heroes respectively equipped with their own legendary equipment when summoned, Naofumi received the Legendary Shield as his weapon. Due to Naofumi's lack of charisma and experience he's labeled as the weakest, only to end up betrayed, falsely accused, and robbed by on the third day of adventure. Shunned by everyone from the king to peasants, Naofumi's thoughts were filled with nothing but vengeance and hatred. Thus, his destiny in a parallel World begins...

The students of class 3-E have a mission: kill their teacher before graduation. He has already destroyed the moon, and has promised to destroy the Earth if he can not be killed within a year. But how can this class of misfits kill a tentacled monster, capable of reaching Mach 20 speed, who may be the best teacher any of them have ever had?