My Unique Skill Makes Me OP even at Level 1 Vol 4 (light novel)

Ryota Sato gets the surprise of his life when he's suddenly transported into another world and nearly clobbered at the hands of the young, pretty adventurer Emily Brown. This new world revolves around defeating monsters and profiting off whatever they drop-food, money, items, and more. Unfortunately for Ryota, he has no skills to speak of...until he learns he has otherworldly drop luck that brings him never-before-seen items! Suddenly his luck turns around...or does it?

Ryota Sato finds himself transported to a world where everything drops from monsters in dungeons.

He and his Ryota Family live their lives venturing into dungeons to sell monster drops. But one day, after rescuing the city of Indole from poverty, Ryota runs into a mysterious girl in the dungeon Aurum.

"A monster?!"

"Nope! I'm no monster. My name is Aurum. I am Aurum!"

Who is this unknown girl, who shares a name with the dungeon she appeared in?!