Legal Question in Real Estate Law in California

I can't answer with respect to Japanese taxes except to say "probably, at some point". However, U.S. citizens residing in Japan remain liable for U.S. taxes. The full extent of such liability is covered in IRS Publication 54, entitled "Tax Guide for U.S. Citizens and Resident Aliens Abroad". I'd guess you'd be liable for income taxes on any rental income you made and capital gains tax if and when you sold it, and possibly an inheritance tax depending on value. You should probably obtain an appraisal of the property value as of the time of inheritance.