I can't help but notice that Nico's stockings don't match. They're the same color, but she's wearing a longer one on her right leg. Now, maybe it's just a mistake, but I'd rather imagine that she just hoped no one would notice because she somehow lost one in the wash.
Actually, if you take a closer look, you'll see that Maki's stockings don't match either.
So the obvious conclusion to draw here is that Maki and Nico swapped one stocking each so they could each have something belonging to the other against their skin.