If you GOOGLE "how to become a Japanese citizen' It sounds like you have to live there 5 years to apply and then wait another year for government red tape and give up your US citizenship among other things. I get the feeling you would need to read , write , and speak pretty good Japanese to make it through the process. Might get better info from other members. I loved Japan and wanted to do what you are talking about also. After about a year and a half , the excitement of life in Japan wore off and by the end of the second year , I was happy to return to Maine. Wish you the best of luck though if you go ahead with it.
Uncle Frank