Freelance Design/Illustration and Visas

So I currently have a humanities Visa, and I have worked in Japan for nearly 5 years as a graphic designer. I am interested in doing a workaround to go freelance. I’ve got a job offer for \280000 a month for a year for freelance design work, and the company is willing to sponsor my Visa. They are a very big, very well-known company, and it seems like I shouldn’t have any issues getting a Visa through them.

However, I want to be making more than \280000 a month, and plan to do so through additional freelance design and illustration jobs. I thought this wouldn’t be an issue since design/illustration work falls under the humanities visa. However, somebody recently told me I might need to be getting permission for this additional work? I’m imagining each job is only going to last a few weeks to a month, and most contracts would likely be short-term.

I also have been offered the opportunity of being represented by an illustration agent. In this case, each job would be payed through my agent, but the work would be inconsistent in terms of pay/hours worked.

Even though the work falls under my category, will I need to be getting permission for each and every job? I was under the impression that immigration looks at you sideways if you do too much work under “資格外活動許可,” but I wasn’t thinking it would be an issue since I didn’t think I needed permission for activities that fell under my category?

I believe you had a similar question last year - did you get any input from your immigration lawyer?