Pope, Nikkei-jin means foreign nationals with Japanese ancestry. Different from Nihon-jin. Issei's are the immigrants. Nisei's are the children of Issei's, meaning second generation. They are the first generation of the host country.
If you are a Nisei or Sansei, there's a special category of visa to enter Japan. I believe many Nikkei folks from Latin America use that visa. This more like an immigrant visa, rather than work visa.
However, if you are an Issei without Japanese citizenship, there is no specific category of visa that allows employment, etc., like Nisei's and Sansei's.
Being a shin-issei naturalized US citizen, I'm looking into a visa under the category of "Spouse or child of Japanese citizen," with my mother as my sponsor. I haven't started the process yet, but I'll let you know how the process goes.
Japanese government do not mind foreign nationals with Japanese ancestry (even in part), but they do not seem to like those of us who were born Japanese but later chose another citizenship just because Japan does not recognize dual-citizenship.
I'm not interested in getting my Japanese citizenship back, but I'm curious to know if Nisei's and Sansei's get preferable treatments in terms of immigration process, including naturalization.