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.

While in pursuit of information pertaining to the world-destroying Truedrakes, Yuji takes a quest to investigate an oddity on an island where masses of powerful monsters dwell. On that island, a super valuable material called Mother Earth's Tears has been uncovered. He goes with a veteran party to dig for it, but the veteran adventurers are sharp and might figure out Yuji's true strength...!