You want a Suica card. It's a stored value card. It won't save you any money. But it's very convenient to use. It's good on all Tokyo subways.

http://en.wikipedia.org/wiki/Suica

Yes get one! It sure beats having to go to the ticket machine every time. It also works outside of Tokyo as well.

Suica is nothing for discount.

if you use train wide area in tokyo by JR line only,

1 day pass is 730yen/adlt,360yen/chld.

or only Tokyo-metoro line, 710 yen/adlt and 360yen/chld. (this does not cover Maihama)

sorry but not sure whats JR card.

Get the Suica card by all means. As mentioned, you don't save any money, but the convenience is unbeatable. You also don't have to decipher the various ticket machines of JR, Odakyu, and the Tokyo Metro companies.

I do not recommend the day passes. The day pass is typically only good for one type of transport so you can't use the JR day pass on a subway (Metro), and you can use the subway's day pass on JR. The 730 Yen pass mentioned above is good for JR only. And you will find that you typically won't ride enough in a single day to warrant a pass.

There is one pass that covers both JR and subway (Tokyo Free Kippu), but at 1,580 Yen, it's not a bargain by any means.

Does the Suica Card has child fare, or are they the same price for adult & child? I could not find the child fare in their website.

And can I use it at the yurikamome to Odaiba?

I don't think a child's card is available without proof of being in school in Japan.

Suica is normaly only for adult. Kids under 12 years old can buy it with any ID card.

You can also use Yurikamome to Odaiba.

Japanese ID card, right?

<<<Kids under 12 years old can buy it with any ID card. >>>

Yuli, is the suica card valid on Yurikamome line?