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Just go to Tokyo. It's the part of Japan that you have probably heard about, with "Harajuku girls" and what not. And Akihabara is pretty much the "otaku paradise/techy land" [lot's of computer and anime related stuff]. Shibuya is super cool for shopping [because of Shibuya 109! ...Shibuya, Harajuku, and Akiba are all parts of Tokyo]
[these are the facts you must consider]
But since Tokyo IS so large, you then would have to decide what *part* of Tokyo or relative area you would want to stay in or you'd be doing a ton of traveling.... which I don't know, I guess might be fun because it would provide you with an opportunity to experience the Japanese subway system...
Shibuya is super cool for shopping [because of Shibuya 109! ...Shibuya, Harajuku, and Akiba are all parts of Tokyo]
But if you want the traditional Japan, Kyoto would be your place since it's like where all the temples are.
I'm sure Tokyo has it's share of temples because it's soooo big, and it's share of less urban areas... but Kyoto would be the more "historic culture" and Tokyo is more "modern Japan" ...So you should probably decide which one fits what you've been looking for in a Japanese city.
Osaka might be a good combo of both Tokyo and Kyoto [not that it's as if it was intended to be a combination of the cities, but it has certain aspects that resemble both Tokyo and Kyoto] Osaka is where all the funny people are though... [majority of comedians]
The Kansai dialect is different from the taught Japanese though [based on Tokyo's dialect]...
...
Yeah, just go to Tokyo. [So you can understand people
Communication is key]
But ultimately it's still your decision and it should be based on your preferences, right? Having other people decide for you is just screwy. You need info to make your OWN decision.
I hoped my info helped.
...Thank you for your time.