you enter the store when you see a black demon girl on top of a stone block with a naked girl and it turned to stone along with the necessary wall

Demon merchant: welcome, friend. please come in and take a look at my wares.

if you're eyeing this Stone slab, I regret telling you that it's not quite ready for sale yet-i'm still in the process of breaking in-

Oh, but it sees that glimmer in your eye... IF your desire is to share its fate, I would be more than delighted to make the arrangements