If you are going to be in Tokyo on a weekend, you can go to Yoyogi Park and watch indie Japanese bands playing live - for free! You just go to Harajuku Station and then walk to the park and you'll see bands playing along the sidewalk outside of the park. From there, you could walk to Harajuku or Shibuya to check out the fashion and shopping.
Not sure how old you are, but Harajuku is more for younger Japanese kids - maybe Jr. High - and Shibuya is a little older - maybe High School and up.
But it's raining this weekend, so no one will be in the park!
