Self employed side job while on instructor visa

Hi everyone !

So I am on an instructor visa working as a teacher.

I have read that you can ask for 資格外活動許可申請 if you want to have a side job in an unrelated field regarding your visa category. In that case you need some proof like a contract for your side job.

How about having a self employed business ? For example if I want to sell things ? Does it fall under the same scope ?

Thank you for your answers !