Somewhere in between Shinjuku and Shibuya you can find the adorable area Harajuku. This is a fashion spot for young people showing of their creative and unique street style as well as a shopping area with many japanese and international brands. Many prominent designers and fashion ideas have sprung from Harajuku and incorporated themselves into other fashion troughout the world.
Besides fashion Harajuku can also offer plenty of interesting restaurants, bars, galeries. You can easily spend one or two days walking around this hip neighborhood. I mostly enjoyed walking around and looking at all cute toys, dols and all sorts of things you can buy as well as adorable architecture. Those cubic houses, totally misplaced and so right at the same time.
