Do you need to file a 国外財産調書 (foreign asset report)?
From the total value of assets you hold outside Japan on December 31, check whether you must file a foreign-asset report.
Overseas bank accounts, securities, real estate, insurance and pension accounts held outside Japan. Japanese-located assets and personal-use items do not count.
If foreign-asset income is underreported, an extra 5% penalty tax applies (reduced by 5% if you had filed).