My Isekai Life 12: I Gained a Second Character Class and Became the Strongest Sage in the World!

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...!

Volume 12 of the My Isekai Life manga series by Huuka Kazabana.