Chikashitsu Dungeon: Binbou Kyoudai wa Goraku wo Motomete Saikyou e

A dungeon suddenly appeared in the basement of the shabby house where two poor siblings, Fuyuka and Haruka live. Delving every day for the treasure and meat that monsters drop, before they know it they have become the strongest dungeon explorers in Japan...!?

(Source: Shueisha, translated)