This shape could exist as a projection onto an upright cylinder, wrapping around the cylinder. The two straight edges go vertically along opposite sides of the cylinder. The curved lines wrap around the circumference. The lines are now straight and parallel on the net of the cylinder.
But we can go further: Imagine taking this cylinder and extending it. Wrap it into a loop by connecting the top to the bottom so it forms a torus (doughnut) shape. This connects both sides of the shape, now all “interior” angles are on the inside of the square, and all “exterior” angles are on the outside. The inside and outside just happen to be the same side.
We could say that vampires don’t have a material body and they just alter the wavelength of light that passes through them to project a living form towards the eyes of living observers. That way they could be visible without having a reflection.
Then they could give themselves a shadow by shifting the visible light from bright light sources into infrared or ultraviolet instead of blocking it as material objects do.