Permanent residency of Japan is a status, not a visa.

The information on the Japanese immigration website is, as always, not clear.

But from talking to friends who have been through the process, I can tell you this:

It is probably a better alternative to citizenship because it allows us to maintain citizenship of our home countries while living permanently here.
(I am a British citizen but permanent Japanese resident... very useful.. I can live in either country.)

You must have lived in Japan for at least 5 years.

You must show that you can provide something worthwhile to Japan.
For example: some skill that is useful to Japan.
Teaching English MAY be enough.

You must have reliable income to prove you can support yourself.. or someone else (husband, wife, parent) must prove that they can support you.

You must have NO criminal record here or elsewhere.

You must complete the application form and include the following:

Koseki Tohon (from city hall showing your name on it)

Jumin Sho (from city hall showing your name on it)

Eigyo Kyokasho or kakutei Shinkokusho (income tax return)

Kazei shoumeisho and nouzei shoumeisho
(from city hall showing you have paid your taxes)

You submit the documents to the immigration office.
The average wait is 6 months.. so you must maintain another current visa while you are waiting.

Lots of patience is required.
NEVER LOSE IT WITH THE IMMIGRATION STAFF!