prepaid cellphone/sim

Hi everyone, thanks in advance...

I am buying a new cell phone after the holidays, and was happy to see the model I want supports UTMS 2100 so I can use it in Japan. The roaming fees are pretty expensive though, so I am trying to decide if I really want to use it.

These are the options I am trying to choose from:

1. use my phone, roaming on Japan's networks
2. rent a phone and/or SIM
3. buy a prepaid phone and/or SIM

(if I missed an option please let me know)

Do you have to be a resident of Japan to get a prepaid cellphone? I am not sure how that works even in the USA. And does anyone know roughly what a cell phone costs?

And, can you get just a prepaid SIM and use it in your own phone? (after having my phone unlocked of course)

If anyone has any experience with using or buying/renting a cell phone while traveling please share!

Now a little info about my needs: I will be staying in Japan for about 4 weeks. I doubt I will need to use the cell phone very much, but it is reassuring to have it. We will be staying at a friend's apartment (no landline) for most of the time, but will take a couple trips that may require hotel stays. There are also a few nice restaurants we want to go to that may require reservations. Beyond that we just need it for emergencies. It would also be nice to have a data plan so that I could check my e-mail from the phone... although I believe the device I want supports WiFi so I may be able to do that without a data plan if I am in a place with a wireless network.

1. use my phone, roaming on Japan's networks
2. rent a phone and/or SIM
3. buy a prepaid phone and/or SIM

1. depending on how many calls you plan on making per day this can be very expensive.

2. You can rent phones and SIM cards at the airport. Docomo, au, and Softbank all have counters at Narita. Docomo rents unlocked handsets that you can insert your SIM into (basically same as 1 above). Softbank rents SIM cards. Costs vary from 100-500 yen per day plus usage.

3. Only residents can purchase prepaids.

Yes you do have to be a resident to buy a prepaid. You can rent a phone at the airport though.

Yeah I was afraid you had to be a resident to purchase prepaid... doh!

Can you rent SIMs at Kansai International Airport? I won't be flying into Narita.

Anyone know about what it costs to rent a sim? I can only seem to find the prices for renting a phone.

Japan doesn't really use the Sim card system- the whole system is different here. I am on my third Japanese cellphone and have never used a Sim card. I'm guessing you can't rent just a Sim card to put in your phone, and that's why you aren't finding that option.

I'm not totally up to date on new developments though so maybe someone with more knowledge can confirm this.

Can you rent SIMs at Kansai International Airport? I won't be flying into Narita.

Anyone know about what it costs to rent a sim? I can only seem to find the prices for renting a phone.

See:
http://www.softbank-rental.jp/

Japan doesn't really use the Sim card system- the whole system is different here.

Today most Japanese 3G cellphones (NTT DoCoMo, SoftBank Mobile and recent KDDI phones) do use SIM cards.