After emerging triumphant from a mystical labyrinth and saving his classmates, Nagumo Hajime sets out with his companions, including the new addition Kaori Shirasaki, to conquer more labyrinths and find a way back to their world. Meanwhile, the heroes of Tortus face a setback and prepare for an impending demon army invasion, learning from their past failures. With the final battle approaching, Nagumo must once again confront both old and new foes, demonstrating his strength and resolve to protect his loved ones.