I Believe these Boxes are sad because they represent Mado's childhood, playing with those Boxes you Fit the Shapes inside, and Madotsuki misses being a baby so she put the sad faces on these in her dreams. The Aztec Rave Monkey was a Plushie she had as a Child.
That might explain the Toriningen Picnic in that area too. While the other kids are having fun together, she is isolated and plays with her toys alone.