You have to fulfill following conditions to apply for Naturalization

Ordinal case

• Inhabit condition・・・have to been having address in Japan consecutively for more than 5 years when you apply for Naturalization
• Capacity condition・・・more than 20 years old and have attained adult age in accordance with your home country's law
• Behavior condition・・・good behavior
• Living condition・・・can live in Japan without living problem
• Prevention multiple nationality condition・・・have not any nationality or is going to lose your nationality by the naturalization
• Observance of the Constitution・・・have never tried and insist and make a group or join to the terrorism against the Japanese government

In case of don't need to fulfill the address condition

• have been having address or living in Japan more than 3 years and children (except adopted) of non-Japanese who were Japanese national
• born in Japan and have been having address or living in Japan more than 3 years, or their father or mother (except foster parent) born in Japan
• have been living in Japan more than 10 years

In case of don't need to fulfill address condition and capacity condition

• spouse of Japanese national who have been having address in Japan or living in Japan more than 3 years
• spouse of Japanese national who have been getting marriage more than 3 years and have been having address in Japan

In case of don't need to fulfill address condition, capacity condition and living condition

• children (except adopted children) of Japanese national and having address in Japan
• adopted children of Japanese national who have been having address in Japan more than 1 year and was under age in accordance with their mother's country law when they were adopted
• people who lost of Japanese national (except lost of Japanese nationality after naturalization in Japan) and have been having address in Japan
• born in Japan and don't have any nationality form the birth and have been having address in Japan

Some of non-Japanese people can acquire Japanese nationality by notification to fulfill following conditions.

Acknowledged children by Japanese father

• acknowledged by Japanese father after birth
• less than 20 years old
• have never been Japanese national from birth until now
• father was Japanese national when children born
• father must be still Japanese national (if the father has died, father must be Japanese national when he died)

Re-acquisition Japanese nationality who lost Japanese nationality because of neglecting of retention of Japanese nationality

• acquired Japanese national and another country's national to born out of Japan, but lost Japanese nationality because of neglected retention of Japanese nationality
• less than 20 years old
• be having address in Japan