When you leave Japan  

In the case where you will leave Japan and lose your domicile and residence for tax purposes in Japan but are still subject to relevant tax procedures, you must appoint a tax agent who resides in Japan and submit a “Declaration Naming a Person to Administer the Taxpayer’s Tax Affairs for Income Tax and Consumption Tax” to the district director of the tax office which has jurisdiction over your place for tax payment. Your tax agent will deal with the tax procedures on behalf of you. 
　You can appoint a Japanese corporation or a person who resides in Japan as your tax agent.
　If you are a resident who must file the tax return for the year in which you leave Japan, the due date for filing the tax return and paying the tax is as follows.

(1)　If you submit the “Declaration Naming a Person to Administer the Taxpayer’s Tax Affairs for Income Tax and Consumption Tax” before departure, the due date for filing the tax return and tax payment for the year is March 15 of the following year.

(2)　If you leave Japan without submitting the “Declaration Naming a Person to Administer the Taxpayer’s Tax Affairs for Income Tax and Consumption Tax”, you must file the tax return and pay the tax before departure.

国税庁タックスアンサーより