Well, apart from the obvious lack of ability to speak the language. To answer your question about what else you can possibly do right now to help your chances a bit: Publish academic papers or do internship at a Japanese company based in your home country. Things like that.

Long-term way to be able to work here (I live in Japan): get a masters degree in Japan, and then go job hunting here. Mind you, job hunting here is not that easy. Most students apply at least 6 months to almost a year before they graduate. To secure a job at the start of the fiscal year

Lastly, this one:

https://www.careercross.com/job-search/result/63532624

I just searched “no Japanese” in the language ability. Lol. i am not sure how many of the companies there are willing to sponsor someone who doesn’t even live in Japan, but it will at least give you an idea of what they’re looking for or something.

Good luck!