Some brands contain katsuo (powdered bonito) as well.
It is used to make okonomiyaki. To the flour, you add your ingredients such as cabbage, egg and water to make your Okonomiyaki.
You can also buy instant okonomiyaki mix, to which you just add water.
Okonomiyaki flour is generally sold in Japan in 500 g and 1 kg packages.
Some people in North America suggest Bisquick as a substitute (sic).