Hajime Nagumo, an ordinary high school student, is transported to a fantasy world along with his classmates as part of a summoning ritual to save humanity from extinction. While his peers are granted powerful abilities, Hajime receives only the basic skill of transmutation, deemed weak and useless. During a dungeon expedition, he is betrayed and left for dead by a classmate, falling into the abyss of a monster-infested labyrinth. Surviving the fall, Hajime undergoes a harrowing transformation, both physically and mentally, as he battles monstrous creatures and consumes their flesh to survive. This ordeal awakens his latent potential, granting him unique abilities and crafting skills that allow him to create powerful weapons and tools.

Emerging from the labyrinth, Hajime becomes a ruthless and pragmatic individual, driven by a singular goal: to return home. Along the way, he forms alliances with various companions, including Yue, a vampire princess imprisoned in the labyrinth, and Shea, a rabbit-eared beast girl. Together, they navigate a world filled with political intrigue, ancient secrets, and divine machinations. The group encounters other classmates who have also been summoned, some of whom harbor their own ambitions and conflicts. Hajime’s journey is marked by battles against powerful foes, including demons, gods, and rival factions, as he uncovers the truth behind the world’s creation and the purpose of the summoning.

The narrative explores themes of survival, betrayal, and redemption, with Hajime’s character evolving from a vulnerable outcast to a formidable force. His relationships with Yue, Shea, and other companions provide emotional depth, balancing the series’ action-heavy plot. The story delves into the complexities of the fantasy world, revealing its history, the role of the summoned heroes, and the true nature of the gods who orchestrated their arrival. Hajime’s journey is one of defiance against fate, as he challenges the world’s expectations and forges his own path to strength and freedom.