"Koro Sensei Quest!" is a comedic fantasy anime spin-off of the popular series "Assassination Classroom," reimagining its characters and premise in a role-playing game (RPG) setting. The story is set in a whimsical, medieval fantasy world where the students of Class 3-E are adventurers tasked with defeating the Demon King, Koro Sensei, a powerful and eccentric octopus-like creature. Unlike the original series, Koro Sensei is not a teacher but a mischievous and nearly invincible antagonist who constantly challenges the class with his unpredictable antics.

The narrative revolves around the students' efforts to level up, acquire skills, and gather resources to defeat Koro Sensei. Each episode features self-contained adventures, often parodying classic RPG tropes such as dungeon crawling, boss battles, and quest completion. The students, led by Nagisa Shiota, take on various roles typical of RPG parties, including warriors, mages, and healers, each contributing unique abilities to their missions. Karma Akabane serves as a rival to Nagisa, often competing for leadership and glory, while characters like Kaede Kayano and Rio Nakamura provide comic relief and strategic support.

Koro Sensei himself is a central figure, frequently interacting with the students in humorous and unexpected ways. Despite being their target, he often aids them indirectly, offering advice or creating challenges that help them grow stronger. The dynamic between the students and Koro Sensei is a blend of antagonism and camaraderie, with the Demon King's playful nature contrasting with his overwhelming power.

The series maintains a lighthearted tone, emphasizing humor and parody over serious stakes. It explores themes of teamwork, perseverance, and personal growth, albeit through the lens of a fantastical RPG world. The episodic structure allows for a variety of scenarios, from battling monsters to solving puzzles, ensuring a diverse and entertaining experience. "Koro Sensei Quest!" successfully adapts the core elements of "Assassination Classroom" into a fresh, imaginative format, appealing to fans of both the original series and RPG enthusiasts.