Yuji Sano was a normal guy working a soul-sucking nine-to-five job when he suddenly found himself transported to a fantasy world where he restarted his life as a Monster Tamer. After befriending the Slimes, Yuji is quickly able to gain a second character class, ranking up his stats and learning new skills as he encounters one surprise after another.

After a hard fight, Yuji manages to come out on top against the Ancient Sage, Reliol, who was being controlled by the Laboratory! And thus, the field trip from hell comes to an end. Upon returning to the academy, Yuji is given the title of honorary professor, granting him access to the Forbidden Archives. With the Spellbook of Etwas finally within reach, Yuji must first figure out a way to combat the mind-pollution that affects anyone who reads it!