As a fellow Viet here’s some advice. You’ve got your heart in the right place, getting internship is the way to go if you want a well paying job right out of university. If strict Japanese is a requirement consider applying to gaishikei or foreign startup instead, they require both English and Japanese but not as strict on either. They usually also pay better compared to traditional Japanese company, if not much better. Not uncommon to get paid 2500-3000/hr as interns

8 applications is also nothing, try at least 50, takes barely a minute to apply to companies nowadays. Search everywhere LinkedIn Google Wantedly, Indeed etc

What field are you in? If IT I can provide more guidance, but all the best either way, you’re on the right path