When you own real estate in Japan and have real estate income, you need to file tax return ( Kakutei shinkoku = 確定申告 ).
If you are not living in Japan, it is difficult to get form to file tax return.
But, you can make tax filing form in website of tax agency in japan.
This is link of their website. ( In Japanese language, though )
If you can not understand Japanese language and need assist of Japanese person, please contact with me.