Should I buy train tickets online to travel around in Tokyo, Japan area?

Question:

I plan on staying in Nerima-ku, Tokyo. I also plan in visiting places like Akihabara, Shinjuku and any other place similar to these. So, I was wondering if I should buy train tickets online (which will cost me almost $800 USD for 21 days and I plan on staying for 30 days) or should I just buy train tickets locally? Thanks for the help!

Answer:

If you are only going within Tokyo, then you can get a subway day pass for all lines for about 1000 yen.
If you want to travel all over the Kanto area, or even farther up to Aomori, then you might look into getting a JR East Pass.
See http://www.japanrailpass.net for more info.
The full JR Pass which you need to get before going to Japan is worth it only for long distance travel across the country and back. If you are staying in Japan for 30 days and only staying in Tokyo, it would be quite a shame - if you haven't seen it all before, it is well worth going - also quick and efficient.