I really had to go prying from my files to get this one. Fact is, we're in a position where we're starting to run out of suitable material. This one is even cropped to hide R-rated lolis.
As for why I picked this one, it's easy to see when you look at it. First, there's the face, nice and shy with a great expression and a fine blush. Then there's the pose. I was introduced to this pose by Seiryuga's Nano Dance series, and it seems to be what certain sources use when they depict a little girl covering her shame. It's a nice pose, very cute and very expressive.