Using Samsung S4 in japan

Hello everyone. I am scheduled to arrive in Japan in August. I will stay there for two years. I want to know if I can use my Samsung Galaxy S4 and blackberry Torch (9800).
Thanks

Yes, but they would have to be unlocked. But if you're coming for two years, you may be better off just getting a new phone on contract.

Kindly help me with price differencial between using S4 or buying a new phone on contract for 2 years. Which one will be better for 2 years assuming I am going to use my phone basically for internet and tethering .

It depends on what phone you want and what discounts you qualify for. To get internet and tethering for your existing phones will cost from about 3000 yen a month on b-mobile depending on your needs. New phones on contracts could potentially cost the same but come with the new phone. Check this out to get started:

http://www.bmobile.ne.jp/lineup.html

Dear Friend,
Since I will be new in the country, there will be no need to call anyone. I would like to use my phone to use internet when I am out and use as a modem for me and my wife's laptops. Of course , Skype to my family in India. I am not in the habit of spending much on internet as in my country it is damn cheap.. (old habit die hard, You know. LOL) In the given requirements please suggest what is good and most importantly, economical for me.Should I bring my S4 or forget it here in India?
Thanks for your prompt reply.
Shambhu

In that case I would look into the various data only options. B-mobile linked above has some of the best offerings, but their page is only in Japanese. You should be able to figure it out though with a good translation site.