The best thing to do is contact the Japanese consulate and ask if you fullfill the conditions of any long term visa.
A quick search, however, reveals one that may suit your purpose:
The linked page describes the further financial and health insurance requirements.
When it becomes clear when you want to go, you will probably have to submit the application in person at the responsible consulate.
Sources:
Credit:stackoverflow.com‘
4 Mar, 2024
4 Mar, 2024