Surely my life next months would be something like:
- 2 months in Japan
- 3 months in Europe
- Back to Japan not sure how long
- Back to Europe? ...

I was also planning to get a smartphone.
I went today to look for them but I was told that any phone I get in Japan will not be usable overseas (unless I use expensive roaming).
So I was told that I can not get a contract overseas, a SIM and just use it on the phone.
I would expect that from a Japan-made Japan only phone but HTC desire?

Also I was told that I would have lots of problems if I buy a (expensive!) smartphone overseas and I try to get a SIM for it in Japan.

Someone has experience on this?

All phones in Japan are sim-locked, so you'll need something that can be hacked.
Many popular keitai have hardware hacks, and the iphone can be done in software (not sure if the iphone4 one is public yet but it's already hacked). Don't know about Android sim-unlocks.

It has nothing to do with HTC etc. All phones ever anywhere support sim-locking, but it's up to the provider if they do it or not. I read that Docomo will be getting rid of sim-locking within the next 2 years though.

I can sell you my 32GB 3GS which is nicely hacked (old bootrom, all firmwares have SHSH blobs recorded, original baseband rom) if you want, then I can buy an iphone4

You could also buy an unlocked phone in Europe and just get a contract /w sim here. There are no problems with using a foreign phone as long as it's on the same radio frequencies. You just need to make sure you set it up correctly. You might also want to limit what you say to the staff at the store when you sign up. Just say you were out of the country for a few years and want to use your old Docomo phone or something.

This will only be possible with a phone that runs on 2100 MHz. Traditionally people have used unlocked phones and Softback as a provider to do this.

I should note that it may be a big hassle to get everything to work.

Here is a thread on a cheap way to get 3G internet on the N900 in Japan. (should work with any unlocked 3G phone) http://talk.maemo.org/showthread.php?t=31680&page=9

Ow, found this last minute:
http://www.dannychoo.com/post/en/25485/J...d+SIM.html

For reference, one of my acquaintances has an Australian iPhone (Australian iphones are factory unlocked, but it's easy enough to do on your own) on Softbank /w a prepaid card. He has no data plan though afaik so just calling & maybe texting.

http://softbanksucks.blogspot.com/
http://mobileinjapan.com/

Wasn't the softbank sucks blog just started because the guy couldn't get all the discounts on an iphone without a long visa? That is not unique to softbank.

In any case, I have no problems on softbank and iPhone works on docomo too.

I think KDDI, DoCoMo, and Softback all suck.

All their plans are way overpriced.

However, when I had to pick, I went with Softbank. I don't remember the details but they are the only provider that offered free Sb-to-Sb calling during some hours. Softbank is also the cheapest, if you want unlimited data and a little talk-time per month. They are also the only provider that can receive international SMS and send free SMS.

And I don't even want to get on the ridiculous prices for talk/minutes.