[Sangetsu]

Some phones sold in Japan can be unlocked and used with a different sim card, but there aren't many of them. None of Docomo's phones can be unlocked, and just a few from the other carriers are unlockable.

Japanese phones also work on a 3G system, and not the GSM or GPRS systems which are common in other parts of the world.

Japanese phones do have lots of features, but those features do not work outside Japan.

If you want a good phone which can be used anywhere (including Japan), look at HTC models.