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.

Tucked in the mountains near the elite Kunugigaoka Middle School lies a small derelict building that houses the delinquents and dropouts of Class 3-E. Looked down upon by their peers, the students in this class appear to have little hope in advancing their academic careers. That is, until the national government tasks them with eliminating the greatest threat to their planet: their new teacher. Having already destroyed the moon, the octopus-like professor—dubbed Koro-sensei—has now threatened to destroy the Earth by March of the following year. In light of their mission, the students have found that killing him is easier said than done. Not only can Koro-sensei move at speeds of up to Mach 20, but he can also resist almost every earthly weapon. Ironically, he also proves to be one of the best teachers Class 3-E has ever had. Training the class to excel in both their studies as students and skills as assassins, Koro-sensei is confident that his students' ingenuity and indomitable will could return them to the main campus. Through trial and error, Nagisa Shiota, as well as the other students of Class 3-E, must figure out Koro-sensei's weaknesses—and fast, for the very fate of the world depends upon it.

To the casual eye, the amnesiac bounty hunter Wu Liuqi looks quite intimidating. With his deadly telekinetic scissor techniques and his ability to seamlessly transform into anything, one would not expect his modest demeanor. In fact, Wu is quite terrible at his job. Often times the freelancer can be found botching an assassination or targeting the wrong person. While his failures could be due to his subpar skills, it usually boils down to him being a normal kid, with a heart unsuited for his line of work. Accompanied by his feathered friend Dai Bo, Wu is on a simple quest to regain his memories. Although his inconspicuous day job as a hairdresser and his after-hours occupation are simply a means for him to repay debt, his various ventures seem to intertwine with his pursuit to recover his lost past.

Extra episodes of Killer Seven.