Teenagers Going to Japan

A member of Japan for Visitors forum asks, "I'm planning on going to Japan for 1 week next year sometime during June or July with 2 other friends. We will all be 18 old males fresh out of high school. We'd like to go to many places like Mt. Fuji and Studio Gibli Museum and many other places...Where are places we can meet people our own age? What is a good guidebook for finding good places to eat and shop around Tokyo?" Suggestions?