A bit lost on how to deal with 個別資格外活動許可

Hello everyone, first time posting here.

I recently moved from Shanghai to Tokyo so I was looking forward to having normal Internet and being able to stream on Twitch.

I made it to affiliate and now I am realizing… this is probably considered a second job and is not covered by my visa (Twitch forces you to submit tax information). My current visa is Engineer/Specialist in humanities/International services.

I don’t have any problem declaring revenue and paying taxes, I just don’t know how to do all this legitimately. I found an agency that claim I need to fill a 個別資格外活動許可 request, but they want to charge 100,000JPY to help which is more than I think I will make on twitch in the next 3 years…

I saw a few threads on reddit concerning this but no conclusive information. Does anyone have advice, information, or can refer me to someone who can help for a more reasonable price?

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Thanks!

edit: added visa type