An embassy staff of a certain country once said he wanted to become a permanent resident and have his son come to Japan to live together. He has lived in Japan for more than a decade and is very fluent in Japanese. He has an Official Visa.
Despite the length of his stay so far, his period of stay is only 1 year. He has always had to renew his period of stay every year due to the embassy’s rule. “Having continuously resided in Japan for 10 years or more, plus having continuously resided in Japan with a working visa for 5 years or more” is required for permanent residency. Plus the period of stay must be the longest allowed for that particular visa which is 5 years. Hence, he is not eligible.
Another question is whether an Official Visa is a working visa. The answer is yes. Hence, if his period of stay is 5 years, he is eligible since he has already lived in Japan for more than a decade.
However, his future plans of life taking the nature of his official duties into account will be carefully screened by the Immigration Bureau once his application is filed.