Guarantor for “Child of Japanese National” visa

Hello everyone,

I moved to Japan last year and I’m currently on an Instructor visa. My mother was born in Okinawa, but moved to America when she was young (around 5 years old). I have an old copy of my family koseki from around 50 years ago and my mother’s name is listed. She should be a citizen, but has no proof of it besides this old koseki. I’m hoping to go to Okinawa sometime soon to get a new copy of my mother’s koseki (or perhaps I can do this over the phone/mail, not sure). I believe my passport and my birth certificate (which lists my mother’s maiden name and birthday) should be sufficient proof to obtain this.

Since I’m already working in Japan, I should be able to use my own income and tax documents for the visa. The main part I’m concerned about is the guarantor requirement. Unfortunately I don’t have the contact information of any of my Japanese relatives. I do have Japanese friends who could guarantee me, though.

My question is: does my guarantor have to be a family member for this visa? The guarantor form seems pretty generic and doesn’t specify that it needs to be a relative. According to the MOJ website, it states “身元保証人には、日本に居住する日本人（子の親又は養親）等になっていただきます”, which seems to imply that it doesn’t HAVE to be my mother and could potentially be any Japanese national. What do you guys think?

I’m sorry for the wall of text. Thanks for reading!