Citizenship in Japan Residence Rules..
Becoming a Citizen of Japan is not easy, and requires a specific residence requirement, together with Language skills and sufficient income.
You are required to have a valid visa (Status of Residence) from the Immigration Bureau of Japan at the time of application and you must have been living in Japan for at least 5 years. Also the bureau confirms whether you have been living in Japan at least 80% of the 365 days every year.
The time spent on a Student visa cannot be counted in this 5 year period.
You need to have sufficient income: whether you can work and earn an income will be checked.
You need to have Japanese reading and writing skills at least equivalent to an ordinary 7 to 8 year old Japanese primary school student.
You need to be a person with no nationality or else forfeit your foreign nationality when approval is given for your Japanese nationality.
The Ministry of Justice, The Nationality Law – Article 5.
The Minister of Justice shall not permit the naturalization of an alien unless he or she fulfills all of the following conditions:
(1) that he or she has domiciled in Japan for five years or more consecutively;
(2) that he or she is twenty years of age or more and of full capacity to act according to the law of his or her home country;
(3) that he or she is of upright conduct;
(4) that he or she is able to secure a livelihood by one’s own property or ability, or those of one’s spouse or other relatives with whom one lives on common living expenses;
(5) that he or she has no nationality, or the acquisition of Japanese nationality will result in the loss of foreign nationality;
(6) that he or she has never plotted or advocated, or formed or belonged to a political party or other organization which has plotted or advocated the overthrow of the Constitution of Japan or the Government existing thereunder, since the enforcement of the Constitution of Japan.
Source: The Ministry of Justice, The Nationality Law – Japan
21.1 - 725,628