Issey Miyake Efficient Square Dress, Black
This dress is wild, it's theoretically made from one big square, with the sleeves and neckline of course cut into the correct shape for fit. So the body flares out into volume when you move, but lies closer to the body when still.
NB on sizing: Pleats Please sizing is inherently flexible due to the nature of the fabric, which stretches generously. The primary difference between sizing is in length.