One of the most important components in Japanese cuisine is katsuobushi or dried bonito flake. Katsuobushi, which is high in umami flavor, is used to make stock and a topping, garnish, and spice for everything from noodles to rice to eggs.
When used as a topping on delicacies like okonomiyaki and takoyaki, they are said to move or dance. If you become queasy when you see moving food, it can be a weird sight at first. It is, however, nothing to be concerned about.