The mysterious giant underground labyrinth Tartaros. There, adventurers day and night venture looking for treasures and other riches. The rookie adventurer Rabi who has challenged the dungeon, due to his bad luck, falls into a trap. It is at that moment when he meets a beast woman merchant Firo, with whom he makes a deal to be her #1 customer.

What will happen on Rabi's adventure? Will he continue to buy items from this beauty!