My Isekai Life 23: 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. The dragon created by the Laboratory was part of a ritual to resurrect Reliol, the only other person in history besides Yuji who was both a Tamer and a Sage. Unfortunately, a massive amount of life force was required for the resurrection to succeed. Upon finding that her rebirth came at the cost of another's life, Reliol teams up with Yuji to destroy the Laboratory once and for all!

Volume 23 of the My Isekai Life manga series by Huuka Kazabana.