Financial Sponsor for Student Visa CoE

Hi everyone!
This month I was nominated by my home university to study in Japan this Fall 2024 and Spring 2025.
As I was trying to gather all the documents so my process would go smoothly I came across what could be, maybe, an issue with my application.
To make things easier, my family and I decided to choose a family member as my sponsor, and the only one who exceeds the minimum income requirement is my step-father. The issue is that he is not my step-father on paper since my mother and him never got married (but they had my younger brother and do live together). So my question is: if this could be an issue and could risk me being rejected.
Another option was me having a company/business sponsor me, since I am the co-owner of a business in my country, but I couldn't find any information about if this could be a viable option (especially because we are talking about a student visa and not work visa) and if this would be a huge risk.

Thank you everyone and have a nice week!

The purpose of the financial sponsor requirement of the student visa is to show that you have a stable/reliable source of money so that you'll be able to afford food, shelter, and the other expenses involved with what you'll be doing in Japan (studying, in your case). Because of that, you might run into some difficulties with the two potential sponsors you mentioned.

If your mother and her boyfriend are not married, the Japanese immigration department will not consider him to be your step-father. That doesn't mean they'll automatically reject him as a financial sponsor, but as you and he do not have any official familial connection, they'll see it as a less secure relationship than if an actual legal relative were sponsoring you.

As for having the company you co-own act as a sponsor, you say that it would be a "huge risk." Generally, the immigration department wants financial sponsors to be someone who can pledge, with a high degree of certainty, to be able to cover your expenses in Japan. If your company's finances are such that your expenses in Japan would be a huge financial risk for the company, it's probably not going to look like a very reliable sponsor in the eyes of the immigration department.

Ultimately, though, these judgement calls are up to the immigration department to make, so I'd recommend asking someone in the immigration department or your country's Japanese embassy/consulate as soon as possible, so that you can look for other options if they say that neither your mother's boyfriend nor your company can act as your sponsor.

I think there is no regulation about financial sponsors. but, as described in the above post, their thinking way is as same as ordinary Japanese way that it is unlikely that unrelated persons become financial sponsors eventually.
to overcome this problem, I think you can ask your step-father to write a statement which promises to help you financially.
he should write the relationship in detailed to convince them. it is preferable that he provides additional documents ( his bank balance and his income certificate).

the second idea has a discrepancy. if your company can be a sponsor, that company has money to pay salary to you. it means, if you have income, you can afford your expense in Japan by yourself. it is enough to show your income certificate and bank balance. (you can be a financial sponsor by yourself.)

Thank you so much for your answers!
It looks like my stepfather may not want to sponsor my stay in Japan, which is understandable after the quantity of papers I�fll need to submit.

As for my company, it does have a enough financial resources to cover my stay in Japan with no worries (even for the company itself) BUT I do not receive anything from it. Everything the company receives goes to the company itself (basically invests in itself).
I have a part-time job and my objective is to work there until September.
My idea is to use the money I�fm saving from my part-time job in Japan and not really the company (just use it as a guarantor)
Thank you again!!

you should think more simply.
immigration asks you who takes care of your financial matters.

you must say to immigration that you come to Japan for STUDYING, not for enjoying your life in Japan, and not for working to earn money for your living expense in Japan. their logic is that you have to spend your major time for studying, you may work a little bit for supplementing some part of your expense, and you can use some times for sight-seeing. you need to write your application following their logic.

your post suggests that you want to live in Japan independently from your parents. that is not their expectation.