Places for a teen/ early 20's to visit

Where in Japan would be a good place for a foreigner that in his teens/ early 20's to visit? I know that Shibuya is supposed to be popular among the youth culture in Japan, but is there any more "scenic" spots?

That's quite a vague question. It all depends on the person and what they are interested in.
Japan is an amazing and beautiful place, why not look through this site and see what grabs your attention.
I first went to Japan in my early 20's and toured all over not just shibuya

well, let's see. Some things that interest me are beaches, electronics, theme parks, music, etc. Somewhere within the cities of Tokyo and Kyoto. My main interest is getting to know about the culture I guess. I also want to be able to talk with other Japanese people freely.

-Tokyo Metropolitan Gov building 0bservatory in Tokyo
-Umeda Sky Building Observatory in Osaka
-Breathtaking nightview from Mt.Maya in Rokko Mountains, Kobe

http://www.yakei-kabegami.com/cgi-bin/photo2/187/4507/sum.jp...

Shibuya: Flashy fashion and Saturday night street musicians

Ura-Harajuku, Daikanyama: Low-key fashion and cafes

Akihabara: Electricity and Otaku

Kichijoji: Big park, little shops and bars

Odaiba: Bayside fairground and game archade

Note that alcohol is legal only for those 20 and over, but most bars allow high teens in as long as you don't drink.

in Tokyo I would add Asakusa and Yanaka for a look at old fashioned areas. Anyone in its late teens-early 20s should likely be interested in history and culture or, at the very least, in something that looks different from the stereotypical views foreigners get of Tokyo from movies.