I think I kinda understand. Kanako starts running because she can be excited, unaware of the dangers that can happen. But once given a warning, she has the sudden reflex of doing the opposite on purpose. Almost like being told not to do something by your parents but you do it, anyway, to annoy them or it just tempts you to doing it more.
oh yea~ They all had to do something and she tripped and hit the camera. I laughed a bit until she started crying... O-O;;;;; and then I laughed again because the others started laughing... O-O;;;;;; ....still funny, though...