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.

As a result of the divine spirits' protection, Agnes has an unusual and often embarrassing power: whenever she experiences strong emotions, she makes mushrooms sprout on people! One day, her royal fiancé, who claims to have dragon blood, breaks off his engagement to Agnes, claiming to have found his true soulmate. Her reputation tarnished, Agnes vows to return to commoner life when she's unexpectedly summoned to a ball by her ex-fiancé's cousin: a prince who is far from horrified by her mushrooming him.

Days before her marriage to the king of the neighboring Sunruta Kingdom, Princess Annabel of Najir is abruptly betrayed by her fiancé and thrown into prison with her magic knight under suspicion of being a spy. After being held captive for months and informed her kingdom is no more, Annabel passes out in a burst of destructive magic, only to awaken as her 12-year-old self, six years before her political marriage. Armed with knowledge of the dark future to come, she now has another chance to bring about a new fate.

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!

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?