This picture is the last, or one of the last, in a series, so to explain this one, I'd pretty much have to explain the rest, and I'm just too damn sleepy for that at the moment. I'm pretty sure I saw the whole story summarized in the comments of another one of the pictures on Danbooru a few days ago; just browse through the rest of the artists' stuff (which would be a good idea in any case) and you should find it.
The woman in the picture is wearing a grass skirt, and nothing else...she's holding a wallet...does anyone want to take a guess at where it's being kept?