which railway pass should buy?

hi..I would like to spend 3days in tokyo and wonder that which kind of railways pass should I purchase.

Basically I will travel around the city of tokyo, karuizawa and hakone.

I need a pass which can use start from Narita airport. Please advise..thanks

3 days in Tokyo as well as Karuizawa & Hakone sounds really packed. You will spend more than a half of your travel time on the train. If that's no problem for you, maybe JR East pass will be recomendable...

http://www.jreast.co.jp/e/eastpass_sp/index.html

If you travel this autumn, the temporarily available flexible 3-day JR East Pass would provide you with savings. If not, regular tickets will come cheapest:
http://www.japan-guide.com/e/e2361_02.html

For transportation in Hakone, you should consider the Hakone Free Pass:
http://www.japan-guide.com/e/e2358_008.html