Daniel,
I've been on these forums for over 15 years. Too many people ask questions like yours withOUT having done their homework.
That's why I ask. My questions were not meant to sound condescending. Please understand that. I mean, you didn't even mention visas in your initial query. You might be surprised to know that many people feel like they can just come here and play in a band anywhere, for example, and not even think of a work visa.
As for the link to immigration guidelines, if you plan to work here, and you understand that you need a work visa, then that site is one of the most important ones you will need because it explains what is needed for obtaining a work visa. Specifically, here:
Immigration Services Agency of Japan
This is the site where most people seem to go for such information:
VISA
...but it has woefully been pared down with far less information than people need, so I rarely post it anymore and give the other one instead.
And, yes, in a sense, you
are immigrating here, even if only for 3 months. People can't just drop in for a week, a month, or 3 months and just start working (or immediately get a work visa). Getting the visa takes time (2-8 weeks).
Frankly, and you may not know this, but you are darned lucky that there is a work visa for that short period of time. It began only a year ago (July, 2012, to be exact).
To all foreign nationals residing in Japan Beginning on Monday, July 9, 2012, Start of a new residency management system!