text: I'd try graphic design, visual arts, take some courses in Japanese culture[hey it couldn't hurt ;-D] and anything that teaches you how to capture the feelings of real people, real things in a stylized manner would get you there.  \nI'm sure you don't need to major in anything.  you need to have a background in creative writing or just be creative enough that a publisher like Viz wants to buy your stuff.  the same thing will apply to the visual aspect.