“Child of Japanese” renewal. Need guarantor?

I will be renewing soon but I’m confused which documents I need. It’s my first time renewing.

I’m not in contact with my Japanese parent so asking them for advice or help is out of the question.

I’m recently unemployed and living off of savings due to medical reasons and it will most likely be like this for a few months after my visa expires. This is why I’m not sure what documents I need to bring. I searched online and saw bank statement would help prove I can live off of savings while healing but wanted to ask here in case I miss something. I am in NHI, and still pay my pension and taxes.

Is having a guarantor letter a requirement or is it okay not to have a guarantor? Do I need other things?

I have my birth certificate to prove my relationship with my Japanese parent since I’m not on their koseki tohon.