Those who are doing side-gigs, side-jobs, side-businesses while employeed what do you do?

Hi guys. I am just a normal foreigner working in Japan, and recently applied for PR, hopefully, it will be granted in 2 years.

Currently, I work in a financial institution, so I get paid decent money and decent retirement plans, so I am more or less set with my life financially.

The job is 9-6, so I was wondering if there are any other ways to expand my income, or to do something more exciting.

I could not think of that much of a plan, the only things I could think of myself was 1) buying a property and do Airbnb, 2) utilising my CPA license, learn how to do US tax preparation at some mom-and-pop shop to do remote tax jobs (if available)

What are some side-businesses or side-jobs do you own in Japan? How did you start and is it profitable and enjoyable?

Would like to gain some insights and hear interesting stories that you guys could share.

Thanks!

In case you need it, my Japanese is Native-level.