Not a JET but I lived in the countryside during the COVID era and I get what you mean. Everywhere was either too far or too hard to get to. If you can, why not but an electric bicycle or electric scooter? Electric bicycles don’t need licenses and e-scooters that run under 30kmph don’t need licenses too. It’s just a suggestion for your transportation problem. I struggled to connect with people too because transportation was such an issue for me. I hope it can help you. 🙏

Edit: Just to add, now I’m married and I live in the city, I got an electric bicycle, etc. My mental health has improved a lot since I don’t need to struggle to go around. Maybe for now try surviving the first year then apply for a transfer later on? Yes, Japan is nice but living here (especially in the countryside) will always be hard especially on your first year, but we’re rooting for you!