By William Wetherall
The accommodation of migrant and native non-Japanese
Japan has, through most of its political history, been a fairly typical territory in terms of its acceptance of migrants from outside its controlled borders. Depending on Japan's status laws at a given time, some Japan-born descendants of such migrants have been considered Japanese, others aliens, at the time of their birth.
Changing extent and porosity of borders
Japan's borders have at times included both marine and terrestrial ports and crossings. Today, however, all formal points of entry, other than the gates of Japanese embassies and consulates in foreign states, are at sea ports located on some of the islands that make up Japan's sovereign territory, now consisting of 47 prefectures.
While designated control points have generally been closely supervised, Japan's borders -- like those of most national territories -- have been fairly porous to those determined to cross them without official scrutiny and permission. This remains as true today as it was a century or a millennium ago, although stowing away or sneaking ashore on an unguarded coast is becoming more difficult, on account of changes in transport vessels and surveillance technology.
Changing reach of Japanese nationality
During Japan's imperial years, the borders of its sovereign domain came to include territories like Taiwan (Formosa), Karafuto (southern part of Sakhalin), and Chosen (Korea). Affiliates of these territories were then Japanese, and they migrated to the prefectures and traveled from and to Japan as Japanese, not as aliens.
Japanese of Taiwanese and Chosenese regionality, who remained in the prefectures after Japan's surrender in 1945, ending World War II, when these territories were separated from Japan under the terms of surrender, were provisionally treated as aliens during the Allied Occupation of Japan from 1945-1952, and formally lost their Japanese nationality when the peace treaty came into effect in 1952. The status of these people today, and of their descendants born and raised in Japan as redefined after the war, are legally tied to the 1945 terms of surrender and the 1952 peace treaty.
Non-native and native aliens
The laws, statuses, and statistics introduced here concern only legal aliens, mostly in "Japan" as redefined by the Allied Powers after World War II. As such, they include people in the prefectures who (1) migrated to the prefectures after their birth, either as aliens or as Japanese who later lost their Japanese nationality, or (2) were born in the prefectures as aliens, or as Japanese who later lost their Japanese nationality.
Note that above two statements about migration to and birth in the prefectures are independent of historical period. In other words, they literally apply from the Meiji period down to the present Heisei era. This is so because, throughout this time, there have been legal provisions for gain or loss of Japanese status within Japan as defined at any particular time.
The distinction between non-native and native aliens is important for two reasons, one legal, the other demographic. Legally, aliens born in Japan have usually had status advantages over aliens not born in Japan. Demographically, the significant presence of native aliens in Japan's foreign population obviates the common characterization of alien residents as "immigrants" subject to "assimilation". Note also that Japanese alien control laws do not define "immigrants" in the sense that this word is commonly used in countries like, say, the United States.
Complexity and legacy
I prefer the term "complexity" to "diversity" because "diversity" tends to be ideologically associated with racial and ethnic identity -- a private matter -- whereas "complexity" embraces not only "diversity" in this "multiculturalist" sense but also diversity in civil status independent of racial and ethnic considerations. The distinction is important because neither race nor ethnicity are factors in Japan's status laws -- whether for Japanese or aliens.
While fashionable to reduce certain nationalities of aliens to racioethnic "groups" or "communities" in current journalistic and academic writing about foreigners in Japan, the racioethnic neutrality of Japan's alien status laws, and the demographic and legal complexities of all nationalities, obviate such singularization of any nationality.
"Koreans" as defined under Japanese law are a case in point -- and not a unique case, for the same could be said of "Chinese" and other categories. "Korean" aliens, like all aliens, are defined solely on the basis of their civil nationality. Putative race and ethnicity are of no account.
Qualifications for statuses defined by legacy laws, however, are important. More important than whether Koreans in Japan are "diverse" in a personal racioethnic sense, is whether they are "complex" as a consequence of raceless laws which differentiate all aliens according to whether their civil status is based on conditions which obtained before the end of World War II, during the Allied Occupation, or after the Occupation.