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.