Your eyes do not deceive you. This is a blouse with a thong attached. It's all one thing.
I assume this is from Europe. What I can't determine is whether it's supposed to keep your shirt tucked in or pull your thong out so it shows.
Another unknown of this garment: is it supposed to be sexy. I think my co-worker, Peter Flugen, summed it up best by calling it, "the mullet of shirts: business on top, party on the bottom."