I don't think that you would carry your Sidekick to Japan. If using it to get email message, this price will be charge for roaming. But you can bring your notebook to use it at hotel which include high speed internet access.
My sidekick and my cellphone will be staying at home. I can access my sidekick email on the computer.... and there will be internet nearby. (Using my dad's macBook)
Oh that's interesting, no wonder u will go there. I wonder, was your father's parent in army?