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 on a quest to clear out an infestation of wraiths haunting a nearby forest, Yuji stumbles on a mysterious laboratory hidden among the trees. With the help of his trusty Slimes, he infiltrates the facility, stumbling on the existence of a shady and incredibly dangerous organization. To make matters worse, they somehow know all about the infamous Monster Tamer, Yuji...