Registering Address on Working Holiday Visa

Hi,

In a couple of months I will be going to Japan on a Working Holiday Visa.
I understand that when I arrive I will be given a residence card at the airport and that, within 14 days of deciding where I will be living, I have to take this to the local municipality to register my address.
However, my plan for the first 6 months is to walk from the top to the bottom of the country, so I will not have a fixed residence until after this.
My Uncle lives in Japan, so my plan was to register at his address, then start the walk.

My problem is that I have found websites online that state that if the householder is a foreign resident, which my Uncle is, I must provide various documents to prove my relationship with them such as birth certificate etc, and some state that a Japanese translation of these documents must be provided too.
Sources:
http://www.mofa.go.jp/j_info/visit/visa/pdfs/guide_living_en.pdf (page 9, point 5)
http://www.soumu.go.jp/main_sosiki/jichi_gyousei/c-gyousei/pdf/eng_pag... (last page, question 2)
http://kokusai.kuas.kagoshima-u.ac.jp/kokusaijigyo_eng/notification_of... (red text)

Does anyone have any experience of registering their address? And possibly even experience registering at the address of a relative? What documents did you need to provide to prove your relationship?

I'm a bit confused about it because how would it work if my Uncle was not my Uncle and was just a friend instead? How could I prove my relationship to a friend? Or would it not be necessary if we were not related?

Thanks for any help,
Joss

householder=世帯主, setai-nushi
it means the head of family.
if you come with your spouse and children, you have to bring the documents which show the relationships between you and your family members. in that case, the office will register them as one family. (you don't need to show the relationship to your uncle. you and your uncle are not a family.)
if you come alone, you don't have any family member in Japan. no document is necessary. you will become a householder.

you can register the same address as your uncle with no documents. (you and your uncle are independent householders at the same address.)

In principle, if you don't have a fixed residence, you don't need to register an address. In your case, though, because 6 months without an address is a very long time, I would still go to immigration to discuss your situation with them.

Thank you very much, that's a weight off my mind!