Sounds like you'll throw good money after bad for some time pursuing this business when not even close to revenue.

Given your mental health issues, it may be best for you to pack up go somewhere with more social support. That might mean staying in Japan but working a regular job. Don't worry about your reflection on foreigners in Japan. In fact, handling mental health issues responsibly is something that Japan needs to do a lot more of.

$50k USD is not a lot of money. You can save that within a few years in many countries.

The brightside is you haven't went into debt. That would make the situation infinitely worse. Unfortunately, your runway has run out so you have to return to a regular job like a regular person.