You could do a cake using black and red as your main accent colors with a Japanese "character" (letter) that symbolizes something important. I'm sure a quick Google search will come up with great sites. You can even do an image search with Google. Also, there are a lot of rubber stamps with Japanese characters. You could buy one of these, stamp the image on a piece of paper, and then blow it up to a larger size on your computer or a copier. This could then be used to make a frozen buttercream transfer (or you can freehand it if you are good at that).
I'm picturing a cake (sheet, square, or round) iced in white with a large Japanese character in black in the center taking up most of the surface. Pipe the borders in an intense red with an Asian-influenced design. You could even use gold luster dust or edible gold leaf to add embellishments.