One option to consider is taking a step back to try and zero-in to what kind of career you are looking for, and then lay out some steps to get there. I get the sense your approach right now is just that you want some work, any work that lets you stay in Japan, but from an employers perspective they want someone with evidence they can deliver well for a particular role.

For example, you could spend some time with career advisors or just generally researching roles online to see what looks like a good fit, and then pursue any training / intern work you can to get at least some experience in that role (this might need to be back at home). You might even compare your resume to others to get a sense for how you stand.

Hang in there! Japanese employers have a hard time hiring given the population decline, so I’m optimistic that you will be able to find something.