In a world where the monsters evolved into a far stronger version of themselves after the appearance of the "Terrestrialization Virus", made monsters far too dangerous for low-level adventurers to fight. Making Summoner and Beast Tamer a "useless class".Greo Astral, a Summoner who just started as an adventurer, aims to be as strong as his father. Due to various circumstances, he'll now find a way to defeat the monster king, the one responsible for the "Terrestrialization Virus".