Request for visa documents in the ward office

Hi,

My parents are going to visit me here because I got recently hospitalized and still and they want to check on me and take care of me while I'm still weak. I live alone and althoigh, I have my good friends here they're quite busy so my parents are very frantic on coming here to see me.

So, they're going to apply for visa here (Visiting relative type) so they can stay here for a few weeks, maybe 2-3 weeks. I'm going to cover their daily expenses here which would make me their guarantor. Based from the website of the embassy, from the guarantor, the visa requirements are the ff.:
-guarantee letter, invitation letter
-certificate of residence (juminhyo)
-income certificate (shotoku shomeisho)
-tax return certificate (nouzeisomeisho)
-bank certificate (kakuteishinkokusho hikae/yokin zandaka shomeisho)

The guarantee letter and invitation letter I can easily make and provide to my parents even when I'm on my hospital bed. The bank certificate I can probably call Shinsei bank to request for it, hopefully. As for the remaining three (juminhyo, income certificate, and tax return certificate), I'm not sure how I can request for them as I am physically unable to go to the ward office.

Now, I'm thinking of having one of my friends reqyest them in my behalf provided that I give them some sort of authorisation letter. Do you think this would work? Or do you have any other possible actions that I can take?

Thank you in advance for your feedback.
(P.S. For those who want to know, I'm from the Philippines so it's required for us to have visa in order to enter Japan)

For "juminhyo" you need to write a power of attorney letter authorizing your friend to do that for you, and your friend needs to take his/her ID, such as health insurance card or driver's license.

This is the format for that letter, by Yokohama-shi, just as an example. (You need to handwrite this one and stamp it. The second page is an example of how that should be filled in.)

http://www.city.yokohama.lg.jp/totsuka/koseki/list/ininjou.pdf

For "nouzeishoumeisho," again for Yokohama-shi, there is a power of attorney format on this page:
http://www.city.yokohama.lg.jp/zaisei/citytax/dl/nouzeishoumei.html
and the form is this:
http://www.city.yokohama.lg.jp/zaisei/citytax/dl/pdf/nouzei/nouzei-sho...

I wonder if you need the "income" one too, because the "nouzeishoumeisho" would indicate the past year's income. But if you need it, this "kazei shoumeisho" (certificate of the tax levied) will indicate the immediate past year's tax amount AND the income amount.

http://www.city.yokohama.lg.jp/asahi/madoguchi/zeimu/kojin-juminzei-sh...

I am just searching with Yokohama-shi, so sorry if I got the ward wrong.