Taxation of online income on Working Holiday Visa?

So I'm planning to apply for a Working Holiday Visa to Japan as an Austrian citizen.

I currently have a small passive income of around 100 euros per month from music streaming services. Will this income be subject to taxation in Japan?

Additionally, I intend to freelance as a coder on Upwork and release some apps during my Working Holiday year. What are the tax implications for income generated from these activities?

I would appreciate any guidance on these matters.