if anda are in Jepun anda may want to visit akihabara and harajuku. Akihabara is the place with L-O-T-S of Manga and Anime stuff. anda sure wanna sheck out a maid cafe. ( try @home cafe in akihabara ) harajuku is the pashion part. Im norwegian so my english is not so well. hope this help =)
For one thing, anda ought to know japanese. After you've got down, anda might as well visit some of the famous attractions. Personally, I suggest going to the hot springs. I find them very relaxing.
Be friendly with others. Never eat while walking around the city, it's rude there. anda must try the sushi there. I can't tell u much but have a good time!