Hello, and please tell me if this has been answered before, I have browsed the forum, but maybe not enough.
I make a living freelancing on the Internet, so I am not *officially* in employment. The benefit to this is that I can work from any place on Earth where there's an Internet connection.
If say, I wanted to permanently move to Japan, do I need to prove that I can afford to? Do I have to go through all the visitor to permanent resident visa change?
Thank you in advance.

This question in particular has not been covered.. but almost all the visas have.. and there is not a visa to cover what you describe.

Visitors are allowed to stay 3 months.

You must have lived here full time more than 5 years to be even considered for a PR.

You would need to get some sort of legitimate work or business visa and conform to the requirements.

Thank you for the answer I will eventually seek some sort of official employment once I get there. The information on this forum has been really helpful.
I will change the topic a bit, though;
I am in a same sex relationship that is equivalent to marriage (recognized by my country and all), so is there any possibility that my partner can apply for a spouse visa?

No, sorry.