Do you need any kind of visa to stay in Japan for 5 days?
 

I have a passport already, do I need to apply for a visa to stay in japan for 5 days? Or can I literally just arrive at the japan airport with only a passport? What kind of paperwork do I need to do?

All you need is a valid passport. You'll get the paperwork to fill out on the plane. You need to know the address of the place you will be staying and the flight numbers and dates of arrival and departure.