Kouki Takagi, a high school student with low stats and considered a so-called mob character, spends his days hunting slimes in a dungeon that has appeared in Japan, all while idolizing his childhood friend, the class beauty. He's just an ordinary explorer, working hard to earn some pocket money.
One day, an unprecedented golden slime appears before him. Perplexed but determined, he defeats it, and in return, receives a Servant Card, a super rare item worth several billion yen that can summon mythical beings!! Summoning with resolve, he conjures forth a Valkyrie—a warrior maiden of unparalleled beauty, seemingly not of this world.
Rise from being a mob explorer to greatness! The modern battle fantasy begins!