Hajime Nagumo, an ordinary high school student, is transported to a fantasy world alongside his classmates as part of a summoning ritual to save the kingdom of Tortus. While his peers receive powerful combat abilities, Hajime is granted the seemingly weak transmutation skill, which allows him to manipulate materials. Ostracized and underestimated, he is relegated to the role of a support member during dungeon explorations. During an expedition into the treacherous Orcus Labyrinth, Hajime is betrayed by a classmate and falls into the abyss, presumed dead.

Surviving the fall, Hajime finds himself in a hostile environment filled with monstrous creatures. Determined to survive and return home, he undergoes a grueling transformation, both physically and mentally. Using his transmutation skill creatively, he crafts powerful weapons and armor, gradually becoming a formidable fighter. Along the way, he encounters Yue, a vampire princess imprisoned in the labyrinth. The two form a bond, and Yue becomes his first ally and love interest. Together, they navigate the labyrinth’s dangers, uncovering ancient secrets and powerful artifacts.

As Hajime and Yue progress, they are joined by other companions, including Shea, a rabbit-eared beastman with immense physical strength, and Tio, a dragon-woman with a penchant for masochism. Each character brings unique abilities and personal motivations, enriching the group dynamic. Hajime’s journey evolves from a quest for survival to a mission to uncover the truth behind the world’s summoning system and the gods who orchestrated it. Along the way, he confronts powerful foes, including other summoned heroes and ancient beings, while grappling with his own moral dilemmas and the consequences of his growing power.

The narrative explores themes of resilience, trust, and the cost of power, as Hajime’s transformation from a weak outcast to a feared and respected figure challenges the expectations of both his classmates and the world’s inhabitants. The series balances action, humor, and emotional moments, with Hajime’s relationships with his companions serving as a central focus. The story culminates in a confrontation with the forces manipulating the world, as Hajime seeks to forge his own path and protect those he cares about.