Pick up a hobby, read a book. Not sure how Japan or other countries are living, but one thing we still have in the USA are public libraries. We can download an app and check out books. For free. There is a lot more stuff at the actual library, but downloading books and reading them for money sounds like something I can retire doing. I take book reading days at my current job. As long as I put in “8 hours” of work they don’t care how I spend my 8 hours.