Add the dry ingredients (cake flour, katakuriko, sugar and baking powder) in a container and mix well.
Add vegetable oil and soy milk. Mix until everything is just about combined. Please adjust the amount of soy milk so the consistency of the batter is a little thicker than pancake batter.
Cover loosely with a lid or plastic wrap, microwave (at 600 W) for about 2 minutes, and it's done.
If you take 2 tablespoons away from your flour and substitute that amount with cocoa powder instead, you can make a cocoa version.