The ordinary life of 17-year-old otaku Hajime Nagumo is disrupted when he and his classmates are summoned to a fantasy world and tasked with saving mankind. While his classmates are gifted with impressive abilities useful in combat, Hajime is belittled for only gaining an inferior transmutation skill that lacks any real offensive power. During an expedition in the Great Orcus Labyrinth, Hajime is betrayed by one of his classmates, plummeting him to the bottom of an abyss. Though he survives the fall, Hajime is faced with menacing monsters and misfortunes that send him spiraling into a grim nightmare. Desperate to live and return home one day, he resolves to fight for his survival—only to meet an imprisoned vampire he names Yue, who is also seeking to escape the labyrinth. Taking an interest in him, Yue and a few others along the way accompany Hajime on his journey to find a way back home, while steadily transforming from commonplace to the world's strongest.

After rescuing his former classmates from the perils of a labyrinth—a mythical place that grants a divine magic to whosoever triumphs over its trials—Nagumo Hajime emerges victorious, while the new heroes of the fantasy world Tortus must face their first major failure. Together with his traveling companions and the new team member Kaori Shirasaki, Nagumo resumes his journey to conquer all labyrinths and eventually return to his original world. Meanwhile, the heroes from Earth try learning from their mistakes and prepare for the demon army's invasion. As the final confrontation looms closer, new and old enemies start setting their evil plans in motion. Once more, Nagumo must prove that he can prevail against the most formidable opponents, all while protecting the ones he holds closest to his heart.

Ten years ago, a fairy by the name of Daisy appeared and asked the child Eiji Hoshimiya what his one and only wish was. Although his wish remains a mystery, the consequences were catastrophic. In an event called the "Great Destruction," the world started to fall apart as everything collapsed and countless people died. Now, Eiji is a high school student whose only concern is his sick sister. He does not remember what he wished for; all that he remembers is that his wish caused the Great Destruction. In the years since that event, thousands of other people have also received abilities to make their heart's desire come true. These people called "Orders" are believed to be evil and are hated by the general public. However, some of these Orders are after Eiji's life in vengeance for those that he killed. Will Eiji be able to survive the numerous assassination attempts? And the biggest mystery of all: what did he wish for, and what were his intentions in wishing for something that caused so much desolation?

The story centers on an introverted high school student named Eiji Hoshimiya with a huge secret—he wished for the destruction of the world when he was younger. Fairies give certain people special powers called Orders, and what Order Users can do with their power depends on their wishes. Ten years after the Great Destruction, Eiji struggles to come to terms with his immense power. (Source: ANN)