Do I need to carry an official ID?
Always carry your official ID with you whenever you go out. If you don’t have it with you when a police officer asks to see it, you will be taken in to the police station for a long, unpleasant experience.
If you are at KCP for just one semester, your passport is your official ID. If you are here longer, you will have a long-term visa. When you land in Japan, obtain a “resident ID card” using your visa.