Has anyone with a Humanities Visa successfully applied for Permission to do part-time?

Hi everyone,

I’m currently a full-time employee in Japan under a Humanities visa. My salary is quite minimal, so I’ve been planning to take on a part-time job to help with my monthly income.

I’ve had interviews with a couple of companies (one in hotel operations and another in marketing), and both technically accepted me for part-time roles—up to 28 hours per week. It was the managers who accepted me.
However, after a few days, HR from both companies cancelled the offers. They said it was due to my visa type and its restrictions.

What’s strange is that neither company mentioned the option of applying for the “Permission to Engage in Activities Other Than Those Permitted by the Status of Residence Previously Granted” (資格外活動許可). I get the feeling they weren’t familiar with the process.

From what I’ve heard from former coworkers, full-time workers can do part-time jobs as long as it's within the same scope as their visa. That’s why I didn’t think I needed that permit when I first applied.

Recently, I’ve been researching the permit, but most resources I find only talk about it in the context of international students. I haven’t found clear info about how it works for Humanities visa holders.

So I’m wondering:

• Has anyone here with a Humanities visa successfully applied for this permit and done part-time work legally with it?
• Can I apply for this permit on my own, or do I need a sponsor/company for the part-time job first?
• Any tips or experience navigating this process would be much appreciated!

Thanks in advance!