Naofumi Iwatani, an uncharismatic Otaku who spends his days on games and manga, suddenly finds himself summoned to a parallel universe! He discovers he is one of four heroes equipped with legendary weapons and tasked with saving the world from its prophesied destruction. As the Shield Hero, the weakest of the heroes, all is not as it seems. Naofumi is soon alone, penniless, and betrayed. With no one to turn to, and nowhere to run, he is left with only his shield. Now, Naofumi must rise to become the legendary Shield Hero and save the world!

Sagara Sousuke isn't your typical high school student. He reads military enthusiast magazines; he responds to questions with "affirmative;" he brings grenades to school in his bag. Though everyone at school takes him for a hopeless military geek, Chidori Kaname thinks there might be something more to him. When their plane is hijacked in the middle of a field trip, Kaname's instincts will prove correct: Sousuke is an elite, mech-piloting mercenary... and he's here to protect her!

A certain college girl who's loved books ever since she was a little girl dies in an accident and is reborn in another world she knows nothing about. She is now Myne, the sickly five-year-old daughter of a poor soldier. To make things worse, the world she's been reborn in has a very low literacy rate and books mostly don't exist. She'd have to pay an enormous amount of money to buy one.

Eve looks like an ordinary 12-year-old girl, but there’s nothing ordinary about her. She has no last name. No parents or guardian. She’s on the run from a dangerous and secretive organization that will stop at nothing to track her down. And most astonishing of all: she’s a robot, a product of Eden Laboratories. When Eve discovers the truth, she realizes everything she thought she knew about herself is a lie. Eve manages to escape, fleeing the lab, the only home she’s ever known.

Naofumi Iwatani continues his adventure in this second volume. But his task is not yet complete and obstacles mount as the increasingly ominous waves of destruction approach. He finds a new friend and new powerful abilities that may prove to be too dangerous for the companionship. Will Naofumi live up to his role as the Shield Hero and save the world from its prophesized destruction? Or will his dark side consume him?